I'm sure that y'all have seen this Lincoln commercial by now:

YouTube - Cat Power :: "Space Oddity" (David Bowie cover)

After some searching I found that it's sung by Cat Power... Here's another couple of her videos - YouTube has a bunch of them, but some are better than others. Can't find her full-length version of Space Oddity (Lincoln commercial), though

Her web site - It has some music clips from her albums:

YouTube - Sea of Love by Cat Power (Acoustic Version)

YouTube - Cat Power on Letterman

YouTube - Cat Power - Lived In Bars