These are available here: https://launchpad.net/bzr-explorer/+announcements. You can keep up to date by subscribing to the RSS feed as explained on that page.
Questions about Bazaar Explorer can be posted to the developers via Launchpad: https://launchpad.net/~bzr-explorer-dev/+contactuser. If you wish to join this team, make a request accordingly via https://launchpad.net/~bzr-explorer-dev/.
Alternatively, you may wish to ask a broader audience by posting to the main Bazaar mailing list. See http://lists.canonical.com/mailman/listinfo/bazaar for details.
If you want to chat in real time with the Bazaar Explorer developers and users, visit the #bzr channel on irc.freenode.net.