Where: irc.freenode.net, on the channel #squeak, of course.
There is an IRC (Internet Relay Chat) channel devoted to Squeak. Its name is #squeak (naturally!), and it's on irc.freenode.net (note their FAQ about IRC services). You can use the Squeak IRC client, IRCe, to reach it.
NOTE: the IRC client was removed from the base image. Use SqueakMap to load IRCe.
The IRCe client included in the 3.7 full image contains a bug. It will produce a walkback the first time you start it up. You should load the latest version of IRCe from SqueakMap .
If you are learning Squeak (and who ever knows it all?), the IRC channel is a great place to ask quick questions that you don't feel like sending to the Squeak Mailing Lists. It's also a great place to go if you just want to escape the world of Java and C++ programmers for a little while and hang out with people who see the light. :)