I use this nightly on my iBook; perfect for listening to audiobooks or tunes as you go to sleep.

i still use this nearly every night, and haven't found another product that does quite the same thing. it also lets me leave my computer running guilt-free if i go out during the day. ... remember Apple's own warning: "Never allowing your display to sleep my shorten its lifespan."

i recommend combining this app with Quicksilver for fast launching.