ClickToFlash is a small plug-in for the Safari browser on the Mac that blocks Flash animations from loading. This not only speeds up web page loading times but also cuts down the work your computer processor and graphics chip have to do running Flash.
You can still view Flash whenever you want just by clicking on the graphic that displays in its place. You can also choose to enable Flash for whole web sites if required.
YouTube clips will play in H.264 video format rather than Flash which is not only better quality but requires less processor power. You can still switch to watching YouTube clips in Flash if you want.
I've installed ClickToFlash and so far it works perfectly. My MB Pro doesn't heat up like it used to when viewing multiple Flash enabled web pages and I can now ignore all sorts of annoying ads. Neat!
Flashblock performs a similar function for Firefox on all platforms.