I just found out about this program, and it's been very useful. Thought maybe it'll be of some use to other people in here, too.

Album Art Aggregator

It requires that you have the .NET framework installed on your computer, which some of you might not be willing to install. It'll just let you run new and possibly exciting (or possibly bland) software which might require it. .NET's size might turn you off to downloading it, though.

Here's another one that probably not as rich functionality-wise but doesn't require .NET (I think).

http://www.uberview.org/