Yes, Guinness is definitely traditional for stews, and with good reason! Its roasted, malty flavors enhance those already present in the stew and take it to whole 'nother level of awesomeness. But Guinness is definitely not the only beer that can be used, nor is it ideal for all stews. Here are a few more to try!
For beef stews, we really like using porters. These beers tend to have a lot of caramelized and toasted malt flavors that work very well with slow-cooked meat, but without going into the coffee-like bitterness of many stouts. Recently, we've really enjoyed cooking (and drinking) the Edmund Fitzgerald Porter from Great Lakes Brewing and the Black Butte Porter from Deschutes Brewery.
German doppelbocks and German-style double bocks would also be an interesting choice for beef stews. They tend to have robust nutty and bread-like flavors with less emphasis on the hops.
When we're making a vegetable soup like minestrone or mushroom-barley stew, we usually go a little lighter. We might still use a porter, but less of it. Brown ales also give veggie stews a nice layer of savory-sweetness, though we'd avoid the "nut brown" ales as they are often too sweet and syrupy for these purposes. Try Brooklyn Brewery's brown ale or the Saranac brown ale.
For all stews, we'll use a half a cup of beer to deglaze the pan and then add another half a cup along with the broth. If we decide we want a little more of the beer flavor after the soup has been simmering for a while, we add more a half cup at a time until it's just where we want it.
What styles or specific kinds of beer do you like in winter soups and stews?
Related: Food Science: Understanding the Maillard Reaction
(Image: Flickr member idovermani licensed under Creative Commons)

Comments (9)
Black Butte Porter from Deschutes is one of my favorite Porters. The hint of chocolate and coffee is there without being overbearing.
That's exactly what I thought - it doesn't always have to be Guinness. My parents found a dark stout from Eastern Germany, called "Mauritius" and it was wonderful in the stew pies:
http://www.lensandlentils.com/2010/01/beef-and-guinness-stew-pie-sort-of.html
If you live in Quebec or just have access to Unibroue beers, Trois Pistoles works really well too. It adds a lot of depth.
I just made beer braised potatoes (mark bittman's how to cook everything vegetarian) with Brooklyn's Brown ale, and thought it was a great fit. Glad to see you guys agree :)
Try a smoked Urbock beer like Shlenkerla to braise short ribs - recipe here: bklynbraised.com
I used Brooklyn's Black Chocolate Stout in a beef stew and it was excellent!
Pale ales are very versatile for cooking.
I made short ribs braised in my homebrewed smoked porter the other day and they were excellent.
I actually used a nut brown ale in a French onion soup I made the other day - you're right that it adds sweetness, but I'd argue that the sweetness works with French onion soup more than others
I think the beer I use most for stew, at least beef stews, is Chimay, the one with the red label. I think it goes back to the first time I made carbonnade, the great Belgian stew made with little more than beef, onions and beer. *drooling*