Edit your HOSTS file to block those crappy ad servers..
It works great, just put the attached file to your windows/system32/drivers/etc folder. (winXP and w2k)
This is no roadkill, it works and is 100% safe. Bloom25 and other techies can verify this I'm sure.
If you're cautious, you can always open the hosts yourself and see what's inside. The method by which it works is that the included hosts list preloads the ip's of adservers dns names into a false location - your localhost. That means that every time a banner tries to open a popup through these locations the request bounces to the 'busy' signal of your localhost and you get 404 file not found instead of some crappy ad.
Another thingy that HOSTS can do for you is to speed up loading your fav net sites if you include them in the hosts file with the correct IP. The difference is not big with broadband, but is there.