I don’t use iTunes near the way Rob does, but when I do I guess I buy quite a bit.
Albums:
Such Great Heights EP: The Postal Service, the Shins, and Iron & Wine
Bryter Layter: Nick Drake
Give Up: The Postal Service
Songs:
Let Go, Frou Frou
Lebanese Blonde, Thievery Corporation
Fair, Remy Zero
In the Waiting Line, Zero 7
University Microfilms International, Stereolab
Basically, I bought the Garden State soundtrack, only I went exploring rather than just buying the album.
Other interests I’ve found: Serge Gainsbourg, Antonio Carlos Jobim, more of The Postal Service, Underworld (maybe), and the other albums by Beck, The Bad Plus, and Stereolab.