I ignore them for the most part. The sites I go on usually advertise chat rooms, online games and cheat sites, and I'm not interested in either of them. Like, right now in the ad above where I'm typing, I have a site for FFXIII Cheats, Job Advertisements (on a site I've used a few times already, to no avail -_-) and a MMORPG called Perfect World. >>

Some of the facebook ones are okay. I've found a few good bands and college courses I'd be interested in by taking a look every now and then. Sometimes a game pops up, but they're usually games I'm not interested in. I make a habit of deleting Twilight ones and marking them as offensive. *shrug*

They just blend into the background to me. I never look out for them.