Chanukah (Hanukah) starts tonight, technically, in Israel it is already Chanukah. It last for eight days and this year it does not overlap with Christmas. Currently, the only major search engine to have a logo or theme up is Microsoft's Bing. Google (even Google.co.il), Yahoo, and Ask.com do not have a theme up yet. Maybe they will wait for tonight or tomorrow, but for now, here is Bing's theme:
We also have theme, sporting driedels with SEO spelled on them out of our name, the Search Engine rOundtable.
Also, Cre8asite Forums plans on uploading this logo shortly for the holiday season:
Forum discussion at Search Engine Roundtable Forums.
Update: Ask.com posted a theme on Saturday, December 12th, see Nick's comment below:
No logo from Google, Yahoo or others.