Class Channels creates virtual chat channels for each character class as well as four predefined role-based channels: Casters, DPS, Healers, Tanks. These virtual channels use the new addon communication functionality of patch 1.12. Essentially, they "ride" on top of the raid and guild channels.
For base functionality you simply install the mod. You automatically join the appropriate channels based on your character class. Chatting in the channels uses a short slash command such as /dr for druids or /ma for mages. You can join other class-based or role-based channels as needed (handy if you're playing an alt and want to stay in touch with your comrades) and you can even create custom channels as you see fit.
By default, class-based channels transmit over both the raid and guild channels. You can override this by prepending 'r' or 'g' to the slash command used for the channel. So if I usually type /dr to talk to all my druid friends, I can type /rdr to talk only to the druids in the same raid with me or /gdr and only my druidly guild mates will see the message.
This addon makes extensive use of slash commands and there's a good chance that there will be a conflict with another addon's commands. For this reason, the slash commands used by Class Channels are completely customizable. You can create additional aliases for your channels if you like or remove slash commands that are interfering with another addon.
All of the addon's settings and functionality are accessible via the /ClassChan command (or /cc if that one isn't already in use)
Currently there is only an English language version. I welcome submissions of additional translations.