http://freshmeat.net/projects/artworkpl/

Extracted art for 1,000 + albums in about 5-10 minutes. I used Musicmatch to add the art to my mp3s. Creates a logfile that lists the folders w/o album art. So you can go back and add the art you missed. By default it resizes the images to 150x150 however you can change the dimensions to whatever you want.