An easy-to-use yet advanced plugin that allows the application of custom controlled potion effects to users. Supports permissions and has a config file for some options. Auto-updates (at your discretion) and supplies a number of commands. For more information, see the BukkitDev page linked below:
http://dev.bukkit.org/server-mods/potioncommands
Development builds (unchecked by DBO staff) are available here: http://199.241.30.86/builds/index.php?id=2