I learned that I can create my own channels on IRC. To this on Freenode, I just do
/join ##channelname
You need the double hash ## for Freenode. Here are some references:
+ <http://www.makeuseof.com/tag/how-to-create-your-own-irc-chat-channel/>
+ <http://blog.freenode.net/2008/04/registering-a-channel-on-freenode/>