I run two online and attend and help run one IRL. I am a cis-female but I think the majority of my friends are probably trans, so for about a year and a half I've been doing it.
I think it's been VERY helpful. The online groups have helped a lot of men and women connect and feel like they always have friends to talk to (some of them don't have many friends who accept them offline) and I deal a lot with crisis prevention. We also help trans brothers and sisters in need if they have financial issues or need donations such as clothing, unused makeup, household items, you name it!