I've got eight right now.
-Doom 3 Resurrection of Evil
-Mass Effect 2
-Mirror's Edge
-STALKER: Clear Sky
-STALKER: Shadow of Chernobyl
-Torchlight
-Fallout 3
-Fallout
I got into a postapocalyptic kind of mood, so Fallout and the Stalkers got reinstalled.
Then I just felt like playing Mirror's Edge again.
Torchlight is just something that's wonderful at killing time, and Mass Effect 2 is not going to get uninstalled for a loong time. It's just too good.