First, prepare to have your mind blown. Then, watch the The Four Chord Song by Axis of Awesome.

http://www.youtube.com/watch?feature=player_embedded&v=5pidokakU4I#at=82


This comedy trio plays 38 pop songs in five minutes using just the E, B, C#m and A chords.  Pick up those new chords, use www.ultimate-guitar.com to look up the below songs for ordering, and you can play them.