Love Pacific low sodium chicken stock (luckily Costco carries it so I can buy 6 at a time for a fraction of what it would cost me at my local grocery store). If I'm using it as a base for a quick weeknight soup, a little Bragg's liquid Aminos really amps up the flavor of the broth.

If MSG is an issue, be aware that many companies use alterative names to sneak in the ingredient. Search "other names for MSG".
http://rense.com/general92/hidename.html
Love Kitchen Basics when I haven't defrosted my own stock from the chill chest.

I think Trader Joe's organic chicken stock is quite tasty--very flavorful and fresh-tasting. I've made my own stock a few times, and honestly I don't find it as easy as so many others seem to. Sure, the cooking the stock itself is easy enough, but in a small kitchen with a limited number of large vessels, I find the straining and decanting a real pain. So I finally gave myself a pass on homemmade stock-making ; ) and use TJ stuff the majority of the time.

Can't stand the Pacific stuff. Swansons is the best by far. Swanson and Knorr have both come out with concentrated stocks that you can use and not have to open a whole box of stock for just a little amount. As with all stock and broth, you have to watch the amount of salt in them.

I wish I could find a store-bought vegetable stock that I like. They all seem to be very sweet and 'carrot-y."

I buy President's Choice Blue Label chicken and beef stock in the tetra packs. It's affordable, tasty and is low-sodium by default, but Knorr's stocks are pretty good too. I also keep Better Than Bouillon in my fridge for when I only need a little bit of broth, or if I think a soup or whatever needs a little more flavour.

Imagine is the only brand I will buy. Did some "research" on different brands (aka looked at the ingredient list) and was pretty horrified at what I found - http://cuttingoutcarbs.blogspot.com/2012/10/8-healthy-foods-with-secret-unhealthy.html. Swanson has cane juice, molasses, wheat flavoring (bad if you're allergic) and even the healthy brand by Pacific contains cane sugar. Imagine is the only one I've found that only contains broth.

Pacific brand Simply Stock. It's just chicken, water, and salt. ALL the other brands have sugar in them, including every single one sold at Whole Foods, and including all of Pacific brands' other varieties of stock, which is infuriating.

Desparately seeking a good store-bought vegetable stock. I don't mind making my own, but hate sacrificing good vegetables that will just be strained out. Sometimes I save vegetable scraps and make stock out of them, but the last few times I did this the results were terrible. Never found a store-bought vegetable stock I liked-- at best they're too sweet and tomatoey, but more often they have a strange, vile flavor that overpowers everything. Usually plain old water is fine in place of stock, but sometimes I think my soups could use the extra depth of flavor that a good vegetable stock provides.

For veggie stock I like Kitchen Basics (comes in a green box).

I rarely buy veg stock. I save my mirepoix bits and mushroom scraps in a big freezer bag and roast them off when it's full, then make a big batch of stock, portion it and freeze. I only have to do this every two or three months. I save a ton of money and love the fact that I am using as much of my produce as possible!

Someone recently gave me Ted Allen's cookbook, and in it he mentions that when you use a store-bought broth to add flavor to a dish, the flavor isn't derived from the broth's meatiness but from its sodium content. He's not suggesting you abandon store-bought broth when you make soups or stews, but if you're substituting it in for water when you make something like a casserole, it really only tastes better because it's saltier.

He recommends checking the protein content. More protein means more flavor from meat (he recommends a brand or two, but I don't have the book handy now).

@jrandall, is Simply Stock a sub-brand of Pacific? Because I feel like when I've used Pacific broth, it tasted much more seasoned than other broths (and particularly oniony) and really changed the flavor of my dishes, so I stopped buying it. I've always liked Whole Foods' 365 broth because it seems more flavor-neutral to me.

Oh man, this is embarrassing, but I love Wolfgang Puck for veggie broth. It just feels weird to have his face staring back at you from the box of broth. I also keep Better Than Bouillon in the fridge for smaller amounts.

We usually have a jar of Tones in the fridge for when we run out of Swanson but Better than Bouillion is really good stuff.

I use a vegetarian powder in a jar, also sold in bullions by Rapanzel that I liked if I haven't preplanned to defrost any or if i am cooking veggie, but I buy and use frozen stock from 3stonehearth or birite. The perk$ of living in the SF Bay Area.

We have these little concentrated gel... things that you put in boiling water to make up the stock, and we use those for the vegetable stock. For the 'meat' stocks, we use Massel stock powder - they also have liquid and cubes, as well as gravy mixes. You could NOT tell that they don't have bits of dead animal in them.

Mutiple boxes of Traders Joe's Chicken Stock are always in my cupboard (the regular - while it doesn't make any sense since the ingredients are the same, I find the organic version to have an unpleasant flavor). One container and one cup of rice is the perfect ratio for risotto. Will have to give the Penzey's a try though...

We use Pacific low sodium for health reasons. The salt content is the lowest I've found. For bouillon, i prefer Herbox.
All this assumes I don't have some homemade stock in the freezer.
@krislegeek: I do that with my veggie scraps too. i have experimented with veggie Stock in the Ratio cookbook. No celery in his stock and tomatoes are optional. Gives a very different flavor to soups and omits a problem ingredient for some family members.