I've found ID3-TagIT 3 to be an invaluable tool for organizing those media files that aren't pretagged & organized from someplace like allofmp3/mp3sparks/MM. It can be a bit daunting at first, but proves to be very powerful and easy to use if you're willing to spend ~30 minutes picking up its ins & outs.
It can pull track information (artist, genre, album, etc.) from freedb.org, rename files based on ID3 information, fill in missing ID3 information based on file/folder names and so much more.
Development of this utility has, unfortunately, stopped. However, with the latest version available, I've never had a problem.
I wholeheartedly recommend it to everyone...(and no, I have no stake in its usage

)
Its available
here.