FightingDirectory.info is a great resource containing links related to Chinese martial arts, Korean martial arts, Japanese martial arts, martial arts services, aikido, karate, taekwando, muay thai, chung moo doe, tang soo do and more.
Wikipedia - Nei chia
Overview of Nei Chi, internal Chinese arts. Details on the history of the term and styles that are a part of it.
http://en.wikipedia.org/wiki/Nei_chia
An online version of the newsletter published by Mike Sigman from July 1993 to May 1994 offering commentary and articles related to martial arts using 'internal strength'. (May 1, 1994)