Well there are several possibilities... A friend of mine uses this chatbox, which seems to use the SQL DataBase (no idea how it works though) : http://smartor.is-root.com/

another way would be to either use an applet or ActiveX (I prefer the applet) and then there is the possibility (I think) to use PHP with IRC, I believe the commands you need to connect to an IRC server are allready included in PHP, never used them though!