The Gatebot documentation is at http://www.psyc.eu/gatebot

Recently similar approaches have been taken by social web apps such as http://jaiku.com/help/im and http://help.twitter.com/index.php?pg=kb.page&id=28

Interestingly they did not opt for the approach of providing login servers and XMPP's ad-hoc command interface

The opensim people have taken a similar approach: http://xyzzyxyzzy.net/2008/05/27/splitting-opensims-chat-module/

http://unfix.org/projects/talamasca/ is a project that is equivalent to using psyced with an active gatebot (talamasca requires an extra ircd however).

See also Gateway for other gatewaying approaches.