These links should provide you with useful information about YaBB and people who support it

YaBB - Yet Another Bulletin Board
http://yabb.xnull.com

YaBB Help - Unofficial Users Help
http://www.yabbhelp.f2s.com

German YaBB Coders - Modifications (in german)
http://www.germanyabbcoders.org

[CV]XXL's YaBB BoardMod Project
http://boardmod.xnull.com