Today is both Earth Day and Good Friday and while no search engines have a special logo for Good Friday, many do for Earth Day.
Google, Yahoo, Bing, AOL, Ask.com and others have special logos for the special day.
Google's logo is animated, so I have attached below a static picture of the logo and a video of me interacting with the logo. As you can see in the video, as I mouse over areas of the logo, I can make Pandas laugh, birds fly, fish swim and so on.
Yahoo has an animated logo only, there does not seem to be a static version of their logo:
Bing has a nice theme for Earth Day:
So does Ask.com:
AOL has a logo:
And we have a theme here too for the day:
I should note, Google only once had an Easter Day logo and it was back in 2000.