Mailing lists and IRC
GHC developers hang out on the ghc-devs mailing list.
The traffic levels vary quite a bit depending on how much activity there is.
GHC developers also hang out on
#ghc channel on libera.chat (not freenode). This is a good place to ask questions related to working on GHC itself; if you have more general questions then
#haskell is probably more appropriate.
Chatlogs can be found at ???(
http://ircbrowse.net/browse/ghc currently serves irrelevant ads)