I finally got irritated enough with some flash ads that I did some googling and rather quickly found adblock, a firefox addon to block ads. It's actually really cool. I spent maybe 15 minutes hitting my commonly-read websites blocking ads and suddenly the internet isn't as annoying.
So anyway, here's the link.
https://addons.mozilla.org/en-US/firefox/addon/10
In most cases you can right-click on something annoying and just choose Adblock (something)... it's easy to block images and iframes that way. When you click it it'll come up with a url... the real trick is to make it general with a *. For instance, I blocked *.doubleclick.* and single-handedly reduced the number of annoying ads by probably half.
For flash you have to got to tools, adblock, overlay flash so that you can left-click on the annoying flash ad, then block that. Anyway, totally worth it, thought I'd share.