Cloister's M:TG price guide.

CrystalKeep, large comprehensive M:TG database. (mirror, one file)

Dragonstudios mirror, home of Apprentice and Magic Suitcase.

MTG E-league mirror, for Apprentice updates and news.

Magic Set Editor for keeping your Apprentice sets up-to-date.

MTGNews, news on all MTG online gaming

Magic WorkStation

Apprentice Hacks (cheating reference)
Backwash official site