In the blogosphere this is actually quite old news (it appeared a couple of days back) but I just didn't have time to write about it. It looks like Yahoo! is testing a product to rival Google's Adsense. Silicon Valley Watcher reckons that this information came from an "informed source at Yahoo!". Furthermore, Andy Baio on his blog points visitors to the blog of Yahoo! product manager, Ken Rudman, which features contextual ads.
"His homepage shows the vertical two-ad format, monthly archives show a three-ad horizontal format, and individual entries show another variation of the horizontal format. The ads have decent relevancy, especially considering its early state."
Andy has identified that the ads are served from a Overture server - further proof that Yahoo! are tesing the market?