There is a Sonic 2Z chat at #sonic2z on irc.mysteria.net.
If you do not know how to use IRC, download mIRC and install it. After installing it, load it up, and you'll presented with a list of servers to join. Instead click on 'Add'. For 'Description' enter 'Mysteria'. For 'IRC Server' enter 'irc.mysteria.net' and for ports, '6667' will do, which is most likely the default. You can ignore 'Group' and 'Password'. After it connects, it should pop up a window on what channel to join, and enter #sonic2z.
You can also try clicking here with mIRC installed.