Chat&Private messaging software?

[adonis]

I want to offer chat and private messaging for my members.

What kind of software is available for Linux?

[candyflip]

http://www.hotscripts.com/PHP/Script.../Chat_Scripts/

[Mr.Fiction]

Saw this running on some site and it looked pretty good:
http://www.realchat.com/

A lot of sites use:
http://www.digichat.com/