El Dorado

PunBB itself (http://punbb.org/) has a great forum with a lot of plugins listed there (http://forums.punbb.org/). There's also http://punres.org/ - and check out the links on the upper-left of the punbb.org site. There's some stuff on there, too, including a PunBB skin generator that makes it easy to customize the colors (http://www.jsand.net/spinkbb/?lang=en).