Dead iichan boards at time of writing:
ib.robtrc.com
/senti/ - Het. Romance
/pantsu/ - Pantsu
/cry/ - Tears
/mugen/ - Mugen
/rag/ - ROnline
/sakura/ - Sakura
/miku/ - Vocaloid
/ghost/ - Paranormal
/doujin/ - Doujinshi
/slpl/ - Self-pleasure
/t-h/ - Touhou (18+)
/tmh/ - TYPE-MOON (18+)
/unc/ - Uncensored

teamtao.com
/kemonomimi/ - Kemonomimi
/neko/ - Nekomimi

moxious.com
/sleepy/ - Sleep

deadgods.net
/hr/- ABe

extra-muffins.com
/b/ - Doodles

iiichan.net
/oekaki/ - Oekaki
/ocs/ - OpenCanvas

benderchan.net
/bijin/ - Bijin
/r/ - Requests

kaede.iichan.net
/tech/ - Technology

kei.iichan.net
/sm/ - Sexy Men