We use mailing lists to communicate with each other. There are several of them to group people with the same interests and too keep the noise down on the main mailing lists.
Please note that you have to subscribe to the lists in order to post to them. Unauthorised mail will be rejected.
The Development mailing list is for all sorts of topics that do not fit anywhere else. There are no strict rules about what can go there and what not, but please think twice about posting anything here. You will usually get no reply at all if it did not fit.
A Special Interest Group (SIG) is a group of people with interest in a certain topic or area. We have them for the bigger topics to keep noise down on the main mailing list. The names speak for themselves.