A modern city that caters to a large population and a few million tourists a year, Stuttgart responds with an excellent range of nightlife establishments. There are plenty of posh lounges, classy discotheques, brew-houses, and much more, proving that, although it doesn't have the the extremes or overwhelming choice that a city like Berlin has, Stuttgart will still handle your late night needs.
The most popular street for the weekend crowd would have to be Theodor-Heuss-Straße near city center, where there is a fine range of hangouts starting near Rotebühlplatz. Zum Paulaner is a classic brewpub featuring the famous Paulaner brand, while T-O12's skyline silhouettes contribute to an ultra-chic atmosphere and the DJ-driven lounge style of Muttermilch is great for a few beers. There are dozens more establishments here as the street works north until it turns into Friedrichstraße, and while some have exclusivity issues (it'll be hard to get in with a large group of guys), most are pretty relaxed.
For the best brewpubs and beer gardens, try the Schlossgarten, which has two, including the popular Biergarten im Schlossgarten. For locally made brews, the selection is actually a bit lacking (being that we're in Germany and all), with only a few places that brew on-site, Sophie's Brauhaus tops among them. Then again, there are plenty of bars that carry regional (or Bavarian) beer staples, so don't feel obligated to do the “authentic” thing. Other bars that have good reputations include Biddy Early's Irish Pub on Marienstrasse (a big English-speaking clientele), Cafe Stella on Hauptstätter Straße (nice outdoor seating all day), and Mata Hari on Geißstraße (vintage style and a wide selection of beers). There are a lot of quality places in the handful of blocks that circle the Rathaus on Marktplatz, so if you can't find what you're looking for on Theodor-Heuss-Straße, this could be a good option.
Other than the aforementioned areas there aren't any big clubbing districts, although if you're looking for live music, the best option is Universum, which is home to the best touring acts to come through Stuttgart. Other clubs that have a bit of soul and unique atmosphere include Keller Club (godfathers of the indie dance scene), the long-standing and popular Boa Club, a mix of live music and DJ's at LKA, and the bigger groove-spaces of Perkins Place and Proton. Then again, if you're looking for a lot to do under one roof, the SI Centrum Event Center on Plieninger Strasse is a surprisingly inexpensive hotel that puts on a few theatrical performances simultaneously and has an in-house casino as well.
For further information on what to do when you are feeling like hanging out with more than your hotel fridge and a few pay channels on the tube, take a look at our individual nightlife listings and start building an itinerary for Stuttgart.