Recently, a good friend from Apple, Jason Bruder, turned me onto a really great Safari plugin called ClickToFlash.
This plugin works very similar to AdBlock Plus, but is focused on blocking Flash. See below for some screenshots.
You can specify to get the H.264 versions (and even the HD versions automatically) of videos from sites like YouTube, and block the really, REALLY annoying Flash ads that slow down your browsing, and can even crash your browser.
* Yes, applications on Mac crash, as does the OS itself.
Here are some screenshots from the app:
link to app page: http://rentzsch.github.com/clicktoflash/
link to github: http://github.com/rentzsch/clicktoflash