So I've recently been using the Tango Icon Gallery, and have been very pleased with the stuff available there. But one thing that bugged me was that the throbber wasn't available in animated gif form. And I googled it briefly, but couldn't find it there either.
So, I whipped out my trusty GIMP and went to work. The result? A animated gif of Tango's throbber (they call it process-working). I made a slow version, a medium version and a fast version, for your pleasure. You can also download the GIMP XCF so that you can make it whatever speed you want - just make sure to get rid of the blank frame at the beginning if you want it to loop.
Oh, and Tango Icons are Creative Commons Attribution-ShareAlike. I've taken care of the attribution, hopefully this counts as sharealike...if not, someone let me know and I'll be happy to fix it.