Winamp is available both as a freeware option and paid-for version, and will handle most file types and help you tackle batch editing of faulty tag information. It uses Gracenote for CDDB look-up (same as iTunes), so expect some degree of manual correction.
MediaMonkey is also available as a freeware and paid-for version, and will also handle most file types. It has, perhaps, slightly more powerful batch tag editing facilities, plus lots of additional stuff (some of which you only get when you cough up the cash) that might be of use to some. I believe it links out to FreeDB for its CDDB look-up - so you'll be looking at some manual correction of tags with this software, too.
For those wanting ultra customisation and who have a technical bent, the best media player by far is
foobar2000. Be sure to visit its
Wiki site for lots of add-ons (.dll files, many of them) which will enhance functionality and bring you hours of fun. The software handles just about anything you can throw at it, loads light and fast, and has powerful batch tagging abilities that allow you to stipulate what YOU want in your tag information. It's also worth downloading
MP3tag to accompany foobar2000, as this smart program is the best free tagging software on the net.
FK