There are reports from WebmasterWorld that Yahoo Search is shuffling their search results. This is interesting, because we normally do not have a Yahoo Search update until the first week of the month.
The last update was on September 6th and we had one on August 1st. Maybe because the Jewish new year is tonight, maybe - they did the update early?
The thread at WebmasterWorld is pretty convincing, in terms of this being a real update. We do not have a "weather report" from the Yahoo Search Blog yet confirming the update. But I am sure it will come soon enough.
There is also a DigitalPoint Forums thread discussing a spike in traffic from one webmaster. Hopefully, you saw a spike in your traffic as well!
Forum discussion at WebmasterWorld & DigitalPoint Forums.