Steam Summer Sale
FWIW The Longest Journey and its sequel Dreamfall are both 75% off at the moment. I've heard good things about these games so I think I'll grab em.
Other cheap stuff I noticed but already own: Braid 50% off, World of Goo 50% off, Shatter 75% off, Trine 75% off, Borderlands GOTY 75% off, Oblivion GOTY 66% off.