Pokésav
Pokésav is a save editor for Generation IV Pokémon games (Pokémon Diamond, Pearl, and Platinum) designed by COM. Pokésav can edit most visible aspects of a Pokémon save file, including trainer data and almost all parts of a Pokémon (including movesets, IVs, EVs, and PIDs). Pokésav also includes a limited PID/IV generator and a wonder card editor. Pokésav can either edit save dumps directly (both 256KB and 512KB saves are supported) or export Action Replay DS codes to provide the same effects as editing the save.
Currently, Pokésav is split between two official builds: one supporting only Pokémon Diamond and Pearl, and the other supporting only Pokémon Platinum. The latest version for Diamond and Pearl is 0.40c, and the latest version for Platinum is 0.06d. Pokesav.org[1], re-directed here (ProjectPokemon.org[2]) currently maintains Pokésav download mirrors for several languages.
External Links
http://pokesav.umimi.com/ - COM's Pokésav page