These are the primary Mesa 3D / DRI mailing lists:
mesa-users - intended for end-users of Mesa and DRI drivers. Newbie questions are OK, but please try the general OpenGL resources and Mesa/DRI documentation first.
mesa-dev - for Mesa, Gallium and DRI development discussion. Not for beginners.
mesa-commit - relays Git check-in messages (for developers). In general, people should not post to this list.
mesa-announce - announcements of new Mesa versions are sent to this list. Very low traffic.
dri-devel - for the Linux/BSD Direct Rendering Module (DRM) kernel modules supporting Mesa’s userspace drivers
piglit - for Piglit (OpenGL driver testing framework) discussion.
You must subscribe to these lists in order to post to them. If you try to post to a list and you’re not a subscriber (or if you try to post from a different email address than you subscribed with) your posting will be held for an indefinite period or may be discarded entirely.
Follow the links above for list archives.
Here are some other OpenGL-related forums you might find useful: