ClickToFlash
HAHA! promoting something I like
As I have posted before I have a very old computer I work with, and most videos on youtube run very badly because flash video uses more power then quicktime and looks crappier for me. But luckily I was linked to ClickToFlash. what it does is makes it so flash files don’t load up right there (until you click on it) on you, and when on youtube a video is played as a quick time file that not only runs better but looks better too (at least to me).
I would say it would be best for all mac users to load this on, more so if you use a laptop because it will use less battery power too.