The Republican Study Committee is the conservative caucus on the right side of the aisle. A bit of history from the RSC website:
The Republican Study Committee (RSC) was founded in 1973 by Rep. Phil Crane (R-IL). The first executive director of the RSC was Ed Feulner, who currently serves as President of Heritage Foundation. The group functioned as a Legislative Service Organization until such groups were abolished under House rules in the first days of the 104th Congress (1995). Dan Burton was the last Chairman of the RSC before it was abolished.Who is in the RSC? The full list can be found here, but the RSC is chaired by Mike Pence. Among the more notable members: John Campbell, Eric Cantor, Steve Chabot, Geoff Davis, Jeff Flake, Jeb Hensarling, John Hostettler, Bobby Jindal, Pete Sessions, and Tom Tancredo.
Shortly thereafter, the group was restarted as the Conservative Action Team (CATs) under new founders Reps. Dan Burton (R-IN), John Doolittle (R-CA), Ernest Istook (R-OK) and Sam Johnson (R-TX).
The four founders rotated chairmanships until 1998 when Rep. David McIntosh (R-IN) became Chairman. Rep. Sam Johnson completed the term of Rep. McIntosh when he stepped down to run for governor of Indiana. Rep. John Shadegg (R-AZ) became the CATs chairman in 2000 and returned the group to its historic name the RSC in 2001. Rep. Shadegg was succeeded by Rep. Sue Myrick (R-NC) in the 108th Congress (2003-2004). Rep. Mike Pence (R-IN) was elected RSC Chairman for the 109th Congress (2005-present).
The RSC has taken positions on a wide range of issues including the budget, homeland and national security, energy and the environment, health care, financial services, international relations, and Social Security to name just a few.
Why is the RSC so important? If you take a look at the roster of its membership, you will find that it trends towards the "younger" more conservative Congressmen. The president of the Heritage Foundation used to be a member of this group, so you'll find that a lot of the conservative interest groups will find the RSC appealing. Most importantly, the RSC are the people behind Operation: Offset, which was the effort to slow the growth of the federal budget.
The RSC's blog can be found here.