Step back, y'all.
Bastion OST - mostly folk-y compositions with trip-hop drums and amazing orchestration
VVVVVV OST - the greatest chiptune you'll ever hear (the sound quality is a bit crap on this Youtube, but ah well!)
Portal 2 OST - available for
free download!
Minecraft OST - incredibly relaxing.
Blocks That Matter - Gold- the OST is mostly just cutesy retro ditties, but this track is unexpectedly beautiful
Robot Unicorn Attack OST - teehee
And some of my favourite OPs/EDs...
Lisa - Will, from Melody of Oblivion
Asian Kung-Fu Generation - Rewrite, from Fullmetal Alchemist
Last Alliance - Shissou, from Ouran High School Host Club
Flow - Colours and
World End, both from Code Geass (Sony have disabled audio on all the full versions of World End! Damnit!)
Also check out the
Samurai Champloo OST - incredibly good hip-hop to chill out to.
God, I hope I got all those hyperlinks right.