Lighthead - Caffeine
Now as you probably haven't noticed (assuming Apple is doing its job) your computer DOESN'T sleep or go to screen-saver when your using DVD Player or w.e Unfortunately web video (like Hulu.com which I <3 or NetFlix Instant) can't tell the OS not to sleep/dim the display/go to screensaver. Want to keep your Mac awake? Give it some Caffeine. With a single click you can turn caffeine on to keep it from sleeping/dimming/etc with out messing with system preferences. Click again and your mac will go back to its usual settings. The icon shows which mode your in and you can even set Caffeine to turn off after a set amount of time in case you forogt after finishing what ever you were doing.
I've been watching a lot of streaming anime on Hulu lately so this is great :D