Jonathan Coulton and Paul and Storm

This one's a two-fer, highlighting two of the better semi-serious independent singer/songwriger(s)(es)(s)(?!) out there

1) Jonathan Coulton You may know his work if you've seen the G4 show Code Monkeys. Yes, he wrote the theme song. He has a lot of listenable and downloadable songs on his site including a Pop/R&B cover of Baby Got Back. Yes, you read that correctly.
2) Paul and Storm They're what's left of the a capella mastergroup known as Da Vinci's Notebook. And they have good stuff too.

Anyways, check 'em out.