I removed Flash from my system's plugin folder:
I do slightly cheat by falling back to Google Chrome if I need to use Flash (since it has it built in). But once I'm done, I simply close Chrome and the resources previously devoted to Flash get freed up. I've been doing this for about a week now, and it's gone well. I'll admit it is annoying to have to remember to switch browsers if I want to watch a video, but for my personal use, it's a minor drawback that I'm willing to deal with.
More info via Gruber: daringfireball.net/2010/11/flash_free_and_cheating...
That said, it's definitely annoying and kludgy to have to switch browsers depending on what content I want to view. Doesn't seem to happen too often (fortunately YouTube lets me view HTML5 video) though.