How do I unclog my dishwasher?
At the botton of the dishwasher, there's probably a basket-like cover over the drain.  You should be able to pop that off, and under there you'll find a nice collection of disgusting bits.  

I used a turkey baster to blast a lot of it loose, then scooped the resulting soup into a bucket, but next time I'll just use a wet-dry shop vac.