The following are some of the bigger Research groups out there and while there are many smaller groups as well, the ones listed are the larger ones as well as the ones I've had the most interaction with as well.
The BFRO: These guys are the oldest of the large group, likely the first as well as being unique among most as being for Profit, which causes some contraversy. They have membership in every state, the major issues I have with them are the for profit thing as well as the sporadic antics of their leader. Other Researchers of theirs I have encountered have been more respectable, but mileage varies. They have several expeditions a year, none are free to my knowledge and that is the source of many a misgiving at one time the beginning fee was three hundred dollars and you had to supply your own gera, food etc. Many including myself find it easy enough to do the same on our own.
The AIBR: Another largely known research group it is under the direction of the Strains, a pair of well known Bigfoot researchers who have a starting point in the BFRO. They take reports from witnesses, but one of the major misgivings I personally have with the AIBR is that they really don't seem to "get out there". I was at one point a member and also found from the inside a potential ground of competing agendas in the shift sad that are bigfootery. Either way they really don't seem to do very much.
Significant Regional Groups: Below are some of the regional groups that I am more familiar with as well, and it should be noted that many of these groups have a very cooperative relationship with one another and might even be considered an alliance of sorts of east coast researchers. Joint expeditions have been held btween several of them.
Sasquatch Watch of VA: A very active group that operates mostly in Virginia, west Virginia and surrounding areas, they are one of the participants in the Joint epxeditions that ere mentioned above.
NESRA: A group focused on the North east, they are active in New England, New York, New Jersey and Maryland, with additional membership in additional states. Nesra is also a partipant in the joint expeditions.
The American Bigfoot Society: A group that was originally under different leadership, but had a second incarnation that is it's present form. It's leadership operates out of Ohio, and it one of the cnetral organizers of the afore mentioned Joint Expeditions. They have additional members throughout the south and have had in the past a relation with the Texas Bigfoot Conservancy, or TBRC.
The TBRC: The Texas based Group mentioned above, they seem to be active primarily in the Big thicket area, and have several promising ongoing resarch projects.
The MABRC: The Mid-America Bigfoot research center is a large group, with members in many areas, but leadership is seemingly out of Oklahoma. In the past their reputation has been one for reporting evidence on just about every outting and there has been some internal dissention as well. I tend to treat these folks with a grain of salt.
The Pennsylvania Bigfoot Society: An active group out of Pennsylvania, they seem to operate primarily there, but have a cooperative relationship with NESRA, the ABS and Sasquathc Watch of Virginia.
The GCBRO: The Gulf Coast Bigfoot Research Center, these folks as far as I'm concerned are best avoided. They seem to be pro kill, and given to the lunatic fringe, that is the basic summary of my opinion on them. It isn't good.