There is a Internet Relay Chat (IRC) channel on the Freenode network (irc.freenode.net) used for support or development of Pure Data.
Server : irc.freenode.net Channel : #dataflow URL : irc://irc.freenode.net/dataflow
This is the main room for Pd-related chat. There is also discussion about other dataflow environments, like Desire Data, Max/MSP, pnpd, etc.
If you already have a client (such as the Firefox Add-On Chatzilla) installed that handles irc:// links on websites you may simply click on this IRC link. Otherwhise you may connect with your browser using Freenode's web based client or pick a client out of Wikipedia's list of IRC clients that serves your needs.
Sometimes there are meeting held in #dataflow.