Google & Yahoo typically do not show off any special logo for President's Day, which is today. But Ask.com and Dogpile are both showing off special logos and themes for the day.
Here is Ask.com:
Yes, that is Mount Rushmore - more details at ask.com/web?q=Rushmore.
And DogPile goes cute again:
Got to love DogPile!
Update: Here is our theme:
Forum discussion at Search Engine Roundtable Forums.