A joint announcement by Yahoo! (NASDAQ: YHOO) and Google Inc. (NYSE: GOOG) scheduled for 1:30 p.m. PDT today, after market close, has rumor-mongers wondering whether the two will be announcing a big deal. Yahoo! has been on the block for so long that even the slightest breeze of news has everyone guessing; this morning, Doug McIntyre wrote that short interest was increasing as pessimists pooh-poohed Carl Icahn's plans.

Michael Arrington at TechCrunch says his sources are insisting it's only a search partnership, a deal that would probably have far less impact on the fate of Yahoo! -- it may signal more things to come, but let's recall that a "global advertising partnership" deal between Google and Time Warner, Inc. (NYSE: TWX)'s AOL in December 2005, in which Google purchased 5% of the internet company, never (yet) materialized into the acquisition many expected.

No major news outlet has the story yet, and there is no announcement on Yahoo!'s investor relations page. After falling 80 cents today, the stock was rebounding quickly on the rumors, at $25.97 at 2:10 p.m.

Update 6:21 p.m.: Microsoft has pulled its $33 per share offer for Yahoo!, and Yahoo! has announced a search advertising partnership with Google. Yahoo!'s stock ended the day down $3.34, or 12.77%, at $22.81.