Pike users mailing list
A mailing list focused on general programming in Pike. To subscribe to the Pike Mailing List, send a message with the word "subscribe" in the Subject: field to firstname.lastname@example.org. The actual list is at email@example.com.
Pike development mailing list
At present, the main Pike development team internal coordination and discussion takes on a mailing list at Lysator Academic Computer Society. Archives are also available there.
Pike chat channel
If you just want to chat idly with other people interrested in Pike, why not give the #pike IRC channel on freenode a try? When you ask for help, please be patient and wait for a reply. People can be busy or simply not in your time zone and aren't always able to respond right away. On the other hand they are usually happy to answer even hours later and don't mind if their response is not immediately acknowledged.