There are several apps on the store to help find live events, but few are as easy and fun to use as Tabeso. Tabeso (for iPhone but it works on iPad) scours multiple sources, making it far more likely that you'll find something fun to do on any given evening. If you're lucky enough to live in a larger city, Tabeso allows you to follow friends and artists and keep tabs on those shows as well.
Tabeso allows you to log in via Twitter, Facebook or email. If you're wanting to get social, I suggest Twitter or Facebook, depending on which you use more. If you do, it'll be easier for you to go through contacts and invite them to use the app.
As you "tab" stuff (pressing the friendly little Tabeso face/logo) your friends will see