I've made my own yogurt in the past, as described above: get some room temperature milk, throw in a small spoonful of commercial plain yogurt, and stick it in an unheated oven to let the yogurt cultures multiply. Works pretty much overnight. The problem i always had was that the yogurt was never quite as thick and "yogurty" as i would have liked it -- knowing what i know now, i think you could just strain it a little with some cheesecloth to thicken it and intensify the flavors.

My parents used to have some contraption that made yogurt, but it eventually went to a garage sale. If you live in a fairly crunchy area, keep your eyes peeled. Something similar might turn up in the 25 to 50 cent range.

Funny, I'd just bookmarked this article from the writer of the NYT Greek yogurt story, about making yogurt at home:

The Back Story | Greek Yogurt Revival

I've been making my own yogurt for a while now and I love it! I have a Eurocuisine machine like the one pictured above, and while you don't need the machine, it does make the whole process easier and more predictable. It's also nice having the individual jars to take to work for lunch. Here's my blog post about it: http://cookingthehardway.wordpress.com/2008/02/07/yogurt/
I've also made homemade ricotta a few times and it really couldn't be easier.

i have been making my own yogurt for a few years now and i love it. i use the eurocuisine pictured above, and i often use yogurt starter. i have found that the higher the fat content, the firmer and thicker the yogurt. my mixture is usually 4 cups whole milk and 1 cup half & half or heavy cream. heavy cream gives you that nice layer of thick cream on top, which is delicious. i heat my milk to almost boiling, then let it cool, mix in the yogurt or the starter, then i incubate for around 8 hours. its fantastic, you should definitely do it.

I've been making yogurt at home for years too. I make Caspian Sea yogurt, which does not involve a machine .. just start with a starter packet and some milk in a sterile container and let it sit on the counter. Then from the next time on you just take some yogurt from the middle of the previous batch and add milk again, let it sit on the counter for a day or so, and repeat :)

Here's a website for it .. I've never used these people so can't endorse them. They just came up first on the Google search: http://www.happyherbalist.com/caspian_sea_yogurt.htm

We make yogurt all the time and have been for a couple years now. We had had so many questions from a post about it (http://www.chezus.com/?p=60) that we are actually in the process of putting together a video with step by step instructions on how to do. It will be posted on our site ...
http://www.chezus.com/?page_id=207

Come dine with us soon.

I make, at least, 2 quarts of homemade yogurt per week. I use a yogurt maker that I picked up at a yard sale (brand new too.) My yogurt maker holds a 1 quart canning jar perfectly. Here's the procedure I use:

Mix 1/2 cup of powdered milk and enough whole milk to make 4 cups. The powdered milk is important if you want your yogurt thick (more milk solids=thicker milk.) You can also use 2% milk, but I would avoid fat-free because it doesn't turn out as well.

Heat the milk in a saucepan to 180 degrees F (I use a candy thermometer) or until milk is steaming, but nor boiling. Take off the heat and let the milk cool until it is 115-120 degrees F or until warm (think bread making temp here.) Hotter then that and you'll kill the cultures.

Once milk has cooled mix in 2 Tablespoons of starter (commercial yogurt with live active cultures.) I freeze yogurt for this purpose in ice cube trays. I just let 1 ice cube (which =2 Tablespoons) thaw while I heat and cool the milk. Freezing does not kill the cultures. Mix the starter in really well, put into a clean jar and then incubate in a yogurt maker for 6-12 hours. The longer you incubate the tarter it will be. Refrigerate before use. Enjoy!

I have also found that you can chain yogurt up to four times before needing fresh starter. I use 2 Tablespoons from a previous batch to make the next up to four times and then start over. I've found that any more then that and the yogurt doesn't set as well.

Here's a website with good instructions and lots of pictures demonstrating how to make cheese:

http://biology.clc.uc.edu/fankhauser/Cheese/CHEESE.HTML

I've used the basic hard cheese method on the site several times with good results. It takes some patience, though--the longer it ages, the better the flavor. Be sure to cover it with a good layer of wax so that it doesn't grow fuzz while it's aging. And you can use the basic method to produce cottage cheese, as well.

I have a much cheaper Salton yogurt maker (1 quart capacity), and I make it with whole milk and/or 2% half and half (my friends think I'm gross). I leave it in about 8 hours, at which point I set aside a little bit (otherwise I always forget not to finish off the whole thing), then strain 2 layers of cheesecloth for 2 hours.

Wow, I had no idea freezing didn't kill the cultures!

I recently bought the yogurt maker pictured above as well. Our kitchen is a pretty active place and this just makes it easy to set off to the side. 8 or more hours is a long time for my oven to be off limits. I very much recommend making your own yogurt.

...The butter link doesn't seem to be working (and ironically it's just what I was looking for, augh!)

Im going to have to see if I can find a source for vegetable rennet and try cheese.

You don't have to use the oven at all to make yogurt. The way I make it and my grandmother made for over half a century, was you bring the whole milk to a near boil (bubbly in the edges of the pot). Pour in a glass jar (I make at least 1 liter of milk) and let it cool a bit, until when you put your little finger in, it doesn't burn but it is very warm. As a started I have always used other yogurt, I use sheeps milk yogurt that has good cultures - Total won't do... Does not have the right cultures. So you rake about 1/2 cup of yogurt and slowly you mix with a bit of warm milk in a small bowl and then pour it into the milk. Close the glass jar tightly, wrap it neatly with a wool blanket or a wool sweater (something old) and let it sit in a warm corner of your kitchen. 4 hours later you got yogurt. The BEST.

I have had a Salton yogurt maker for years, and it has five 6-oz. containers with lids. I just love it! I make mine pretty much like Charise above described, except I heat the milk up in the microwave, using the temperature probe thing. I always use 2% milk and it turns out fine. I also use a probiotic powder starter I got at a health food store. It cost about $10, but you only use 1 tsp. per batch and it makes 30 quarts.

Thanks so much everyone! Going to try yogurt tonight, and probably ricotta on the weekend.

I used to make all our yogurt and learned this trick from a friend who taught dairy science.

After heating the milk, and adding the yogurt starter, put the mixture in a wide-mouthed thermos flask overnight, or all day.

Easy peasy, and no extra equipment cluttering cupboards and counters.

I made my own yogurt in college, and it's really easy. I'm not sure why you would need a special appliance to do it.

Heat the milk in a saucepan without boiling it. Transfer the milk to a glass baking dish. Add some plain yogurt and stir. Cover with a tea towel, and put it in the oven overnight.

A friend of mine from Turkey once made me a yogurt sauce for pasta with mint and tomato paste. She said her family ran out of yogurt once, and it was a domestic emergency. The neighbors gave them some more to make a new batch, and everyone survived the ordeal.

empress - butter is easy. my 5 year old cousins do it all the time. put cream in a tupperware and squeeze the lid on tightly. give it to 5 year old and let them shake away with it - then take it from them and eat it. :D

or you could use a blender ...

I can really recommend the DIY ricotta/farmer's cheese. My hairdresser recently told me this was how his family made cheese all the time in Athens. I gave it a try and it was both really easy and really good. (I wasn't even expecting ricotta-like when I made it so that was a bonus). My tips - he said to strain/sieve the milk and lemon mix through a clean pillow case. (I used an odd shaped one I'd never used from IKEA and it was perfect, if you have no cheesecloth) and to add the lemon as it moves from simmer to boil (so no need for thermometer). He recommends adding herbs (dill or mint) to ring the changes.

And, of course, I missed out his main instruction/tip - the best full fat milk you can find. Preferably direct (!) failing that Rachel's Organic, or similar (in GB)

Hey, SleepyDweller, check this out:
http://biology.clc.uc.edu/fankhauser/Cheese/Rennet/Rennet.html

According to the link, the active ingredient in the rennet you buy nowadays is produced by bacteria, not the stomach of an animal. So it may be easier to find than you thought!

Soy yogurt!

I make my own in the above Eurocuisine machine. I've been long disappointed with most soy yogurts out there...way too sweet and loaded with filler gums.

So far I've had great success using Vitasoy plain (sweetened) original plus a cup of added plain Silk yogurt. Yes, I still have to use bought yogurt but one big tub lasts a long time and makes lots of yogurt.

I follow the manufacturer's instructions, boiling the soymilk and using milk that does contain some sweetener. The resulting soymilk has a delicate texture, tangy-sweet flavor and a wonderful clean smoothness much more like good quality cow milk yogurt than the pasty soy stuff out there. I've also strained it and made some great frozen soy yogurt too!