Here's a good one on the topic of Shavuot. I give it a B in viralness (or should that be viralocity?). It's a shameless plug for Yeshiva University's Torah Online program, which has lots of shuir (lectures) on Shavuot and other topics.
They should have, and didn't, given credit to the artists. I'll see if I can track down the info.
UPDATE: Someone left a note in the comments section that the artist is: shlomo katz http://www.shlomokatz.com
Hat tip to YouTube user silbermintz for posting the video.