There are a few of them. A plethora to say. Some of them are struggling with lack of members and activity, others prosper, but they pretty much cover everything to do in Sirius.
The choice is mainly yours.
Want my advice? Go for the Rogues. They are cool, and operate in the center of the sector.
I am building one now.
Well I have been building it for a while I have not been recruiting untill I get funds
and finish RP and Speak with Admins with permissions and other things.
Register and make an account and
Give me a PM if you are interested.