Before, during, and after the conference, you are encouraged to participate in the meta-conference on IRC. Freenode is the official IRC network of ApacheCon. ApacheCon attendees tend to congregate on #apachecon on irc.freenode.net.
There will also be per-track IRC channels, called #actrack1, #actrack2, #actrack3, and #actrack4.
Note that general technical questions about the Apache webserver are usually held on #apache. Many individual ASF projects also have project-specific channels where they discuss technical or community issues about their projects.