John Baez occasionally has little puzzle-questions up at "The n-Category Cafe"; in the most recent, he asked who Rambam was. Rambam, of course, is Maimonides; he's not to be confused with Ramban, who is Nahmanides. Both are to be distinguished from Ralbag, who is Gersonides. And if you don't know who Maimonides, Nahmanides, or Gersonides were, I will mock you mercilessly, as well as remind you of this post and this other post.
Virtually all the rabbinical acronyms you could want can be found at Rav-SIG.