for the ones liking flashblock I can also recomend
http://adblock.mozdev.org/.
You can block whatever ads with wildcard url matches.
Install, restart, right click on a banner, "Adblock Image", modify the url to cover what you think seems reasonable, enjoy.
Get the bleeding edge from
http://adblock.mozdev.org/dev.html, which not only blocks but stops them from loading totally + supports regexp matching.