If you watch video on the Mac, one of the annoying things that always seems to happen is that the screen dims at some point in the video. Caffeine is a cool little application that sits in your menu bar to keep this from happening. I see there is a previous tip for it. If you haven't tried it, it's worth trying. If you are a current user, you should check out the newest version as it has a new feature that makes it a lot more useful. Now when you set your screen to not dim, you can give Caffeine a timer as to when to turn itself off. That way, you don't need to remember to turn it off after your video is done. This fixes the one problem I had with it, is that if you forgot to turn it off, your screen was always on.