ListApp plugs you into local events and gigs that you’re likely to be interested in. You can have a browse through what’s happening, pick something of note, and wander along to learn more about the city you find yourself in.
There are stacks and stacks of categories in here, covering all types of music, comedy, eating out and drinking experiences, so you certainly shouldn’t be short of something to do unless you’re in the middle of nowhere. You can get alerts about events in advance too.