In March 2007, Google Israel had a special logo for today's Jewish holiday, Purim. Last year and today, there is no special logo at Google Israel or Google or any of the search engines that I looked at, including Yahoo, Live.com, Ask.com, or even DogPile.
But that is okay, we have a special theme live for the holiday. Here is a picture of it, but you can see the whole theme live at the Search Engine Roundtable:
We also had a theme last year and a picture of that is over here.
Maybe Google will have a logo in 2010? It is a fun holiday and they can go wild with the logo, if they like.
Forum discussion at Search Engine Roundtable Forums.