I haven't noticed any malware of any kind but the last few days I've heard 'Congratulations, you've been selected for a free iPod'. I didn't see any ads my mouse could have rolled over to trigger it so it could be an audio ad that is launched OnLoad in the body tag of the HTML. That is annoying.
Advertising is taking over the web and is in fact the entire business plan behind Google. It will only get worse. Years ago I thought about having a website that was nothing but banner ads as a kind of super electronic billboard. Don't be suprised if something like that arrives in the near future and the browser automatically redirects to it when you type in an invalid URL.