Have you cycled the tank? If the tank hasn't gone through the nitrogen cycle for a few weeks it won't be ready for fish and anything you do add may well keel over or start suffering from debilitating problems.
http://www.theaquariumwiki.com/The_Nitrogen_Cycle
http://www.fishforums.net/index.php?showtopic=113861
http://www.practicalfishkeeping.co.uk/forum/showthread.php?t=5322
That extra time while it cycles you can use wisely to research fish suitable for your tank. Your tank isn't the hugest so be careful.
http://www.theaquariumwiki.com/Stocking_a_Peaceful_Community_Tank
Also, everything, except the Goldfish, Josslyn mentioned was saltwater, and a lot of them, even if that was a saltwater set up, would need a far larger tank. She just reeled off some random fish names courtesy of nemo, and a few made up ones...