As of December 2009, the number of MRAP variants and subvariants in service or being developed for the US military stood at 28, including the new M-ATV. The links provided are to the Globalsecurity.org site's main pages on the variants in question. There are additional links on those pages to information on the programs. I try to keep them more or less up to date. Any errors in the information here are my own.
The US Army's Program Executive Office Combat Support and Combat Service Support had been designated the joint program office for the MRAP program. Of the systems listed, only the M-ATV was listed as being at Milestone 6, Full-Rate Production. The rest of the vehicles were listed as Milestone 7, Operations and Sustainment. It would appear that so far, once an MRAP type has been accepted, there is no rush to phase it out.
An additional two vehicles were still being managed by the Program Manager for Anti-Mine Systems. This office had been the organization first bring MRAP type vehicles into inventory before the official start of the MRAP program in 2007.
The managed programs and systems directory for PEO CS&CSS can be found
here (PDF).
Between 2002 and 2004, the US Army awarded contracts for the purchase of 25 Buffalo mine-protected vehicles through a company called Technical Solutions Group.
United States Army / Buffalo / 2003 / 2+4 men /
LINK
These vehicles were procured as part of the Ground Stand-Off Mine Detection System (GSTAMIDS) program. Also acquired under this program were the Meerkat and Husky Mk I mine-detection vehicles. An improved Husky Mk II replaced both the Husky Mk I and the Meerkat components of the system by 2007. By 2008, the a variant of the Husky equipped with a ground penetrating radar detection system was fielded, referred to as the Husky Mounted Detection System (HMDS). The USMC is known to have borrowed some Husky vehicles for operations in Afghanistan in January 2009 and to have expressed interest in acquiring its own. A further improved Husky Mk III vehicle was introduced sometime in 2009.
United States Army / Meerkat/Husky Mk I / 2003 / No Passengers /
LINK
United States Army / Husky Mk II / 2007 / No Passengers /
LINK
United States Army / Husky Mk II HMDS / 2008 / No Passengers /
LINK
USMC / Husky Mk II / 2009 / No Passengers /
LINK
US Army / Husky Mk III / 2009 / No Passengers /
LINK
Around the same time as the initial purchases of the Meerkat and Husky, the US Army made the decision to purchase a limited number of RG-31 MPVs as control vehicles for the GSTAMIDS vehicle team of Meerkat/Husky and Buffalos. The US Army acquired the first 9 RG-31 vehicles between 2003 and 2004.
United States Army / RG-31 / 2003 / 2+6 /
LINK
In 2005, the US Army and USMC began investigating vehicles to transport engineer and EOD teams and provide them with additional protection against hazards they were increasingly facing in Iraq. The Medium Mine Protected Vehicle (MMPV) and Joint Explosive Ordnance Disposal (EOD) Rapid Response Vehicle (JERRV) were procured in mid-2005 for this purpose. The MMPV was more or less a COTS Force Protection Cougar 4x4, while the JERRV was a Cougar 6x6, which had been modified for the purposes of carrying necessary engineering/EOD equipment. JERRVs can be identified by various stowage boxes other 6x6 Cougars do not have. In the USMC, the vehicles were referred to as Hardened Engineering Vehicles (HEVs).
United States Army/USMC / Cougar 4x4/Cougar 6x6 / 2005 / 2+8 /
LINK
In November 2006, the Mine-Resistant Ambush Protected (MRAP) vehicle program is formally initiated. It issues its first contracts in January 2007. The vehicles selected in its two categories, one for a 4x4 vehicle to conduct patrols and other missions being carried out by up-armored HMMWVs, and a 6x6 vehicle to conduct various support missions, are the Force Protection Cougar, International (later Navistar Defense) MaxxPro, Land Systems OMC RG-33L, Stewart and Stevenson Tactical Vehicle (later Global Tactical Systems) Caiman, and the Force Protection Buffalo. By June 2007, the Land Systems OMC RG-33 had been added to the Category I procurement. The RG-31, and an improved RG-31A1 are also procured later under Category I. The Buffalo was later moved to a Category III for vehicles tailored to dealing with IEDs and Mines.
United States Army / MaxxPro / 2007 / 2+6 /
LINK
United States Army / Caiman / 2007 / 2+10 /
LINK
United States Army / RG-31A1 / 2007 / 2+6 /
LINK
United States Army/USMC / RG-33 / 2007 / ? /
LINK
United States Army/USMC / RG-33L / 2007 / ? /
LINK
In mid-2007, the MRAP JPO initiates work on an MRAP II program. This was in response to the increasing threat from Explosively Formed Penetrators (EFPs). Around the same time, a crash program to upgrade the armor on existing MRAPs to defeat these weapons comes into existence as well, the MRAP Expedient Armor Program (MEAP). The MRAP II program does not lead to any additional vehicle procurement directly. None of the vehicles apparently meet the desired requirements. However, Global Tactical Systems did offer a 4x4 Caiman "Light" as part of the program which was subsequently procured as part of the basic MRAP program as a standard Category I vehicle. The MEAP modifications become integrated into existing and new production vehicles. These are generally represented by an A2 designator, MEAP designator, or Plus designator, depending on manufacturer.
United States Army / Buffalo A2 / 2003 / 2+4 men /
LINK
United States Army / Caiman Plus/Caiman Light/ / 2008 / 2+10 /
LINK
United States Army/USMC / Cougar 4x4/Cougar 6x6 A2 / 2008 / 2+8 /
LINK
United States Army/USMC / RG-33/L Plus / 2008 / ? /
LINK
United States Army / MaxxPro MEAP/Plus / 2008 / 2+6 /
LINK
In early 2008, the US Army also successfully tested its Self Protection Adaptive Roller Kit (SPARK; a mine-roller) on the RG-31 series vehicles. This roller kit was also deployed on HMMWVs and 5-ton trucks.
United States Army / UA HMMWV w/ SPARK / 2008 / ? /
LINK
United States Army / RG-31/A1 w/ SPARK / 2008 / 2+6 /
LINK
United States Army / M900-series w/ SPARK / 2008 / ? /
LINK
By Mid-2008, the US Army and USMC have begun procurement of a further improved RG-31 series vehicle, the Mk 5E. This vehicle is also referred to as the RG-31A2. The RG-31A3, which I believe is the Mk 6 vehicle, was procured further after that, but it is unclear when. I'm also unclear when Navistar Defense released the MaxxPro Dash, a lighter weight, higher performance version of the standard MaxxPro vehicle.
United States Army/USMC / RG-31 Mk 5E/A2 / Mid-2008 / 2+6 /
LINK
United States Army/USMC / RG-31A3 / Late-2008? / 2+6 /
LINK
United States Army / MaxxPro Dash / 2008? / 2+4 /
LINK
Almost all MRAP vehicles have been fitted with, to some degree, remote weapon stations. The types fitted appear to be either the XM101 CROWS or XM153 CROWS II. This appears to have started in early 2008. Variants of the RG-33 family have also been procured specially configured for special operations use since the beginning of the MRAP program.
United States Army/USMC / RG-33L Heavily Armored Ground Ambulance (HAGA) / 2007 / ? /
LINK
United States Army/USMC / RG-33 USSOCOM / 2007-2008 / ? /
LINK
United States Army/USMC / RG-33L USSOCOM Armored Utility Vehicle (AUV) / 2008 / ? /
LINK