We've been keeping an eye out for good products to recommend for folks wanting to tackle baking this year. The idea of self-rising flour seemed promising at first, but it didn't end up being quite what we thought...
As it turns out, flour being marketed as "self-rising" (or "self-raising," as it is called in the UK) is simply regular flour with baking powder added. The ratio of ingredients is usually about 1 1/2 teaspoons of baking powder per cup of flour. Many brands also add a pinch of salt for each cup of flour.
So the "rise" in this case doesn't actually refer to the traditional rising and proofing of yeast doughs. It refers to the rising that happens in the oven as the baking powder becomes activated by the liquids in the batter and the heat of the oven.
Self-rising flour is sometimes used in recipes for quick breads, biscuits, and other baked goods that use chemical leaveners to rise, but it's best to only use this flour when the recipe specifically calls for it. Otherwise, it's all too easy to throw off the proportion of baking powder and salt in the recipe and end up with an under- or over-leavened baked good with off flavors.
In general, we'd say that it's not worth buying self-rising flour, even if you're completely new to baking and are hoping to buy yourself a bit of insurance. And if you're attempting anything with yeast, definitely stick to the plain old flours. Self-rising flour would really throw off your results!
Related: Weekend Cooking: Bake Bread!
(Image: Flickr member kt.ries licensed under Creative Commons)
Red-and-Pink-Stripe...

I hate self-rising cake flour, and in this part of the world, it's the only kind of cake flour I can find!!! (France/Switzerland)
My stash of North American cake flour is gone, I am galloping through my White Lilly (that's a White Lilly label above...) all-purpose which is half-way to cake flour... hope I find some soon (the problem is that people really don't bake much at home)
I have always wondered about self-rising flour, but didn't really know what exactly it was or when to use it! Maybe I'll just steer clear all together--it seems like something that would just sit at the back of the cupboard!
So how does this mesh with Faith's post earlier today for the biscuit recipe with two ingredients, one of which is self-rising flour? Use it? Doesn't make a difference?
I made a South African milk tart a couple weeks back, that specifically called for self-rising flour. It was my first time ever using it. I'm guessing it's a regional thing? I've only ever encountered self-rising flour as an ingredient in biscuits & not much else.
Remember that you can make self-rising flour by adding about 1 1/2 tsp baking soda to regular flour (all purpose or cake). Add a little salt if the recipe doesn't call for it. Much easier than buying something that will sit around in the back of the cupboard!
nigella lawson's recipes commonly use self rising flour for her baked goods so i always have some stashed in case i get a hankering for one of her delectable cakes!
Indy Jeffrey - For Faith's recipe today you do want to go ahead and use self-rising flour if you have it. That's one of those times where if the recipe calls for it, use it.
If you don't have self-rising flour on hand and don't feel like buying it for one recipe, you can do as RebeccaCT says and add baking soda and a dash of salt to regular flour - though that makes those biscuits a 4-ingredient recipe!
Baking POWDER, people, not soda. Baking soda requires an acid to rise, which would mean the flour would not be self-rising when liquid was added (you would have to add an acidic liquid such as buttermilk or citrus juice). Baking Powder contains cream of tartar (an acid) along with the sodium bicarbonate (baking soda), which then reacts to create gas when combined with a neutral liquid. Remember the old elementary school volcano science fair project.
Self-Rising flour is often used in cornbread and biscuit recipes, and is just a shortcut for for a series of other ingredients as many people have stated.
Beer Bread, which was mentioned here recently, http://www.thekitchn.com/thekitchn/holidays-christmas/last-minute-gift-idea-beer-bread-mix-ungift-guide-2008-072215, becomes a four ingredient quickbread with self rising flour: http://www.foodnetwork.com/food/recipes/recipe/0,1977,FOOD_9936_15495,00.html.