A few 'light' albums that I find work quite well as background music.

BT - Binary Universe

Rhian Sheehan's - Standing In Silence

Emancipator's - Soon It Will Be Cold Enough

Jose Gonzalez - Veneer and In Our Nature

They're all albums that you can just let play through. They also work well for getting to sleep. Out of all of them "Soon It Will Be Cold Enough" is the most upbeat with a hint of Hip Hop. "Binary Universe" has some amazing orchestral bits but seems to mix pretty much every genre out there with electronica. "Standing In Silence" is similar to "Binary Universe" but a bit more watered down. It seems a little happier to me as well. Jose Gonzalez is Jose Gonzalez. Remember the Sony Bravia advert where they dropped 250,000 bouncy balls down a San Fransisco street? It's more of that music. Quiet, acoustic guitar.

Enjoy!