Some Bradley lineage:
The original M2 IFV (Infantry Fighting Vehicle) and M3 CFV (Cavalry Fighting Vehicle) were fielded in the early '80s
In the mid '80s came the M2A1 and M3A1 versions which included the larger turret bustle stowage rack, guards around the driver’s and commander’s periscopes, an NBC system for the crew (not the troops in the back), side firing ports deleted, and some other minor changes.
Just before Operation Desert Shield (Aug '90 - late Jan '91) the upgraded M2A2 IFV and M3A2 CFV with armored side panels and some other upgrades were introduced. Most units received new M2A2 and M3A2 versions in the deserts of Saudi Arabia before kicking off the ground war (Operation Desert Storm) in Feb '91.
Following Operation Desert Storm, lessons learned led to the updated M2A2 ODS and M3A2 ODS versions, which were the versions used during the invasion of Iraq. Externally, it looks pretty close to a standard M2A2 or M3A2, but had more armor, improved seating, and other improvements. Most of these were MWOs (Modification Work Orders) added to older M2A2s to bring them up to the new standard. Some were new build M2A2 ODS Bradleys. See the discussion above about the Tamiya and Academy M2A2 ODS kits for more on them.
Around '07, the latest version M2A3 and M3A3 were introduced. These include individual blast survival seats for the troops in the back, digital instruments and commo systems, a thermal viewer for the commander, camera for the driver, and a few other improvements.
There are/were a couple other Bradley variants as well.
The M6A2 Linebacker ADA vehicle was fielded and served in 3ID during the initial invasion of Iraq. Shortly after that they were taken out of service and were all converted back to standard M2A2/M3A2 ODS vehicles.
Before the M6, there was the BSFV (Bradley Stinger Fighting Vehicle). It looked like any other Bradley from the outside, but had a modified interior layout to hold two dismount Stinger gunners and extra Stinger missiles. The idea was that the gunners would jump out and engage targets as they presented themselves.
There is also the M7A2/M7A3 BFIST (Bradley Fires Integration Support Team) vehicle used by artillerymen to plan and execute FA and mortar fires for an Armored or Mech Infantry company. The A2 version looked just like any other A2 Bradley with the rear of the TOW box blanked off as it held targeting electronics. It also had a couple added antennas on top of extended rear light guards and a cable reel holder on the right rear sponson box. The interior is also different with a large operator’s chair and computer console and more radios, along with other FA gear in the back.
The M7A3 BFIST has all the other features of an M2A3, but with a new targeting box in place of the TOW box and the modified rear cabin. In the Targeting Box is a GVLLD (Ground/Vehicle Laser Locator Designator) targeting unit that assists with target location, range-finding, and designating for laser guided munitions.
The M270 MLRS is also based on a lengthened Bradley chassis.
As was the M4 C2V (Command and Control Vehicle) which was tested in OIF, but not accepted. All have been rebuilt back to M270A1 MLRS, except the below vehicle (and a few others) now on display at Ft Stewart, GA.
The USMC AAVP-7A1 RAMS/RS has Bradley running gear and automotive parts.
The newest is the AMPV (Armored Multi-Purpose Vehicle), which is a turretless Bradley that is set to replace the venerable M113. These vehicles are being built and fielded now. It will have five versions.
General Purpose Vehicle (APC)
Command Post Carrier
AMEV (Armored Medical Evac Vehicle) 4-patient (ala M113)
AMTV (Armored Medical Treatment Vehicle) 6-patient (ala M577)