Automatically Rate Your iTunes

Autorate will automatically rate all your songs based on a simple formula (that's even posted on the site). It uses the number of times you play songs, skip them, etc. to rate them. Note that running it will overwrite any previous ratings you might have. Probably not the thing if you have lots of ratings, but if you're just starting to rate songs, this would give you a great jump start. Oh yeah, and it's free.