My favorite software for blocking popups and ads is AdShield. It's the only IE popup blocker I've seen that works without crashing or intruding on resources. It's very lightweight, yet very powerful.

It also has a pretty novel way of working... it blocks based on a substring of a URL. So for instance, you can add the substring "/ads/" or "ads." or ".adserver." or "/banners/" or whatever you like to its blocklist, and it will block the entire URL that contains that substring. The ad is never even downloaded to your cache, the request never goes out of IE.

It also has a whitelist, so that if you want to block popups for everything except sites containing "www.riocar.org", you can do that, too.