My new favorite bookmark is wikigifs.org, a website that shows you each gif on Wikimedia Commons one at a time. You press the space bar to move to the next random gif, and you can see what Wikipedia pages (if any) use the gif. It's like Wikipedia's random article button— but just gifs. The site reminds me just how much work goes into Wikipedia by dedicated volunteers who are committed to making information available for free, for strangers.
Here's another favorite: a hypnotic gif displaying the globe effect.