Gnash has three mailing lists hosted at gnu.org. Archives of these lists are stored at http://lists.gnu.org/pipermail/:
firstname.lastname@example.org is for discussion of gnash development, porting to new platforms, and ideas for the future. This is the best list for technical questions, requests for support, or general questions on usage.
This list has moderate volume. To subscribe, go to http://lists.gnu.org/mailman/listinfo/gnash-dev.
email@example.com is for announcements only. New alpha and stable releases are announced here.
This list typically has a low volume. To subscribe, go to http://lists.gnu.org/mailman/listinfo/gnash.
firstname.lastname@example.org is where summaries of changes committed to the source repository are automatically posted.
This list has a fairly high volume. If you wish to see these changes as they happen, subscribe at http://lists.gnu.org/mailman/listinfo/gnash-commit.
#gnash on irc.freenode.net
The #gnash channel on irc.freenode.net is where many of the developers hang out.
Announcements about Gnash and most other GNU Software are made on <email@example.com>.