Hello and welcome.
There's a sticky thread at the top of this page with all the RPSG/VGs in it but it's starting to show its age now. Pious provided a good summary of the major ones around at the moment in this thread:
http://uk.boards.cityofheroes.com/showfl...e=0#Post1356799
You're always welcome to come and have a browse around The Militia's forums which also incorporates The Cadre, their villanous counterparts as well. Good luck finding one that suits you. 
@Dante EU - Union Roleplayer and Altisis Victim
The Militia: Union RP Supergroup - www.themilitia.org.uk
The Corporation is a very active and friendly villaingroup I'm in, contact me via forum PM or in-game to my character 'Rumour' and I'll set you up.
As Dante kindly pointed out, I've mentioned six good teams worthy of a second look and those are all heroes. There are a few popular villain teams as well. Here is a list of those I know, with brief descriptions of what I think the teams stand for and roughly what their numbers are. Hope this gives you a better overlook of the union heroes and villains RP community.
Guardians of the Earth are a small team of brave and mighty sentinels, based in space orbit, guarding the planet from local and intergalactic threats. From a growing roster of 12 heroes, there are currently 4 core members.
The Militia is a team of citizens who volunteer to defend the city from crime, gangs, outlaws and terrorists threats. From a roster of 26 heroes, there are currently 18 core members. Mutant characters are popular.
New Heroes Union is a collection of heroes who strive to protect our dimension from domestic and alien threats. From a growing roster of 82 heroes, there are currently 28 core members. Magic characters are popular.
Art of War is a group of highly trained warriors from England who now use their skills for global operations. This group mainly plays out-of-character and only a few members are roleplayers. From a growing roster of 84 heroes, there are currently 18 core members. Science characters are popular.
Unity Vigil is an organization formed to help heroes and provide a networking group to liaise with government and non-government organizations. I'm not a member of this team so I can only approximate a number of 12 core members, and hazard a guess at a roster of 48. I think Technology characters are most popular.
Shield Police is my own project supergroup with a growing roster of 12 heroes and 4 core members. We are designed to work with Paragon City's Police Department. Our mission is always making Paragon City safe for all the people we serve. We cut crime and the fear of crime while upholding the Law. Our vision is to make Paragon City the safest major city in the world. A lot of Natural characters but all have an interest to work with Police.
The Corporation are quite simply top of the market mercenaries who will get the job done for the right price. They're not just guns and muscles though, they have good characters all round and interesting action dramas. I would have to hazard a guess at 44 members with 16 core players. Technology characters are popular.
Court of the Blood Countess is a massive nest of monsters of all kinds. Literally. They have ghosts, witches, vampires, demons, zombies, great big mutated freaks and everything else that goes bump in the night. All of them in allegiance to a powerful vampire witch, the Blood Countess. I can guess their roster at 82 members with maybe 18 core players. Magic characters are popular.
The Cadre is a small secret organization operating from a stripclub in Port Oakes. They work as agents of a hidden master known only as Mr Mason but on his off days, the gang operate as freelance criminals. Probably a roster of 24 with 12 core players. Mutant characters seem to be most popular.
The Hyenas are a rag tag assortment of monster hunters making money from the capture, or extermination of the various strange creatures that plague the Rogue Isles and Paragon City. It's a small gig with probably 4 core members from a roster of 12. Natural characters seem most popular.
The Dusk Spiders was originally created by loyalists Doctor Bolt and Omega Chief as a semi-rogue Arachnos unit but has evolved over time to become a mostly autonomous Arachnos division. I would hazard a guess at 12 core members from a roster of 32. Wouldn't be surprised if Science characters were most popular.
New World Alliance however is a global coalition of villains currently being set up by the chaos-monger Dr Edward Mechano. With help from me, this alliance is set to function by communicating on an in-game global channel. It is basically a gathering of ideas, visions and opinions of all the characters across the Union Universe who wish to benefit from chaos and destruction.
What is not known or at least rumoured, is that behind the scenes, there is a lot of political influence and exterterrestrial interferances involved, much of it linked in with the secret sect, the Midnight Illuminati who are said to bent on moulding a new world order upon Earth.
So far we have four villain groups in agreement and several other bad guys interested in sharing their doomsday plans and resources. We think it will be a major plot device for community-wide roleplaying and zone events and you're welcome to join us, regardless of which supergroup you're working with. I hope this helps.
Thanks for the list guys, I'm gonna work on a concept or two to fit in.
I do like the idea of the NWA thing though.
Just back into the game and i've always regretting not taking part in RP as much as I'd l;ike to. So I'm looking for a VG or SG that actively roleplays but its also willing to accept a newbie into the fold.
I'm happy to make a new character around the concept of the group.