Download one of these free IRC Clients if you don't have one.
Note: You need to be a registered user with freenode.net before you can send private messages. This is to block spam. This is pretty simple, see http://freenode.net/faq.shtml#privmsg for instructions.
Kenai offers an integrated chat service for NetBeans 6.7 users. Check it out!
You can also use the IDE itself as a chat client. The Developer Collaboration plugin is a full-fledged Jabber (XMPP) client that lets you create public and private chat rooms and maintain a friends lists. Developer Collaboration comes with added features for developers: It supports live NetBeans project sharing and syntax coloring!
Read how to install and use the Developer Collaboration plugin. You must either set up a private Collab Server or use a public one.