Pixelmon Mod 1.6.4

Features:

172 pokemon
Modifies NO base files (Meaning it should work with any mod)
Configuration file to change spawning amounts, Block and item ID’s
Comprehensive attack system featuring over 500 attacks (including status effects and stats modifiers)
Pokemon overlay showing current pokemon and their status
Functioning pokedex
Multiplayer supported! (no bukkit)
Full PC storage system!

Download: http://www.5minecraft.net/pixelmon-mod/