Rube Goldberg machine video contest
I've been working on some really fun books lately, and among those was Tony Mullen's Introducing Character Animation with Blender. This book is sneaky-good; not only is Tony an excellent writer and teacher, but because the DVD contains the entire Blender application (it's open-source, meaning distributed freely), the book actually serves as a complete kit to start from absolute scratch making your own digital animations.
The Blender community is small but very active and very vocal. They recently held a contest for animations of weird and complex machines--Rube Goldberg devices--and the winning videos are a lot of fun. The desk chair in the third-place video is great, but I like that the first-place winner uses good audio as well as animation.