By now, most of you have probably noticed ads like this on the site (also in the skyscraper zone):

Google has partnered with Tribal Fusion, the company that takes our excess ad inventory and slides in banners. What Google has done is very interesting, and worth noting: they spider the site, analyze it for keywords, then dish up Google AdWords that are appropriate to that page, very similar to what you see when you do a search on Google. These ads are highly targeted, and I've found some pretty cool stuff by clicking on them, so you may want to do the same.