In addition to the versions of Gnus which have had their releases coordinated by Lars, one major development has been Semi-gnus from Japan. It's based on a library called SEMI, which provides MIME capabilities.
These Gnusae are based mainly on Gnus 5.6 and Pterodactyl Gnus. Collectively, they are called “Semi-gnus”, and different strains are called T-gnus, ET-gnus, Nana-gnus and Chaos. These provide powerful MIME and multilingualization things, especially important for Japanese users.