Websites come and leave, but the newsgroup has been the operation center for the roguelike world for almost as long as it has existed.
There you will find a very active and friendly usenet newsgroup dedicated to the development of roguelike games and the discussion of ground-breaking ideas for new projects.
It is advisable to read the Roguelike Dev FAQ before posting.
There are two ways to get access to USENET newsgroup rec.games.roguelike.development.
By google groups web interface
Google provides access to rgrd but it is of poor quality. Spam protection is on low enough level to make finding topics started by regular members difficult and annoying. When posting through google groups do not wrap lines to be shorter longer than 72 columns. It is done for you automatically. Be on your guard. This interface makes it easy to break netiquette unintentionally.
Please remember rgrd is an USENET board. Calling it a google groups forum is faux pas.
This is the preferred method of access. Low amounts of spam and possibility to set up cross-posting or follow-up when needed. A common news service provider among rgrd denizens is Eternal September. An example of a good email/mailer program is Thunderbird.
There is an IRC chatroom of the same name, prefixed as #rgrd.