The unfortunately named Bloxorz is loads of fun. Clearly it should have been called "Blockotron" or "Slabflip 2000", but I guess it's too late for that now. The idea is to get your block slotted into the hole (and in the game!) without tumbling to your death. I know how you hate Flash games, but believe me when I say you'll like this one: there's something slightly misleading about its perfect geometry, and the odd pulsating noise in the background makes me uneasy... Also I'm not sure what's going on with the orange squares, so it might be best to read the instructions instead of shouting "yeah, yeah" and throwing your arms in the air, like I did.
Found at the peerless TIGSource, of course.