I don't have any of these yet, but I suggested neverthless Libris Mortis because it is quite various in the content (both 4 players and 4 DMs), and the theme of undead is generally very common in D&D. If that's not true in your homebrew, Monster Manual 3 is generic therefore easily adaptable but also it's only for the DM, while Frostburn is various in content but it will obviously require you to set the adventures in cold places to use it.