ProximitySpawner
This is a very simple plugin. Upon use of /proxspawn, a random number of zombies (0-6) will spawn around (5-15 blocks) every player on the server.
This was created for the custom spawn system used on MelonCraft Zombies (play.meloncraft.com)
I may add more/update the plugin if there seems to be demand for it, as well as maintain for future bukkit versions (although it is simple enough that it will not need updating)
No config (yet!)
Please contact me if you want the source code.
Great plugin!