Well I can think of the following just of the top of my head. I assume that you are looking for converted military airliners not purpose built airplanes like the B-52 etc.
You have the 707 in service as the E-3 AWACS, E-8 JSTARS. The Air Force in fact is having a hard time finding enough 707 airframes to make the number of JSTARS they want. The E-6A is a Navy version for the TAMPCO mission running radio gear for submarines. Also everyone knows the Airforce one versions I belive they are desiginated VC-137.
B-727. This is the C-22 in airforce parlence. There are a couple assigned as hacks transports in the reserves out of Andrews.
B-737. T-43. These where built as navigation traingers for B-52 navigatiors. Got to go through one they had on static display at Reno-96. Some have been converted to VC configuration. Ron Brown was killed riding one of these. A couple have also been convereted to PAX seating and assigned to an Air Force contractor EG&G and fly support personel to the Air Force facility at Groom Lake (AKA area-51). The Navy has ordered a combi version of the -700 to replace it's C-9 that are in service. It may be interesting to see if the airforce does something simular for its C-9 fleet.
B-747 E-4B these are airborne command posts for the nucular missle forces. And everybody knows that Air Force one is a 747. Both of these versions are on a -200 airframe. At one time the Congress was pushing to have the Airforce to buy a number of freighter versions of the 747-400 because they where cheaper than the C-17. This didn't happen. And there is the proposed laser carring 747 that they want to build for missle defense.
B-757. These are also new airforce aircraft. designated C-32. They are to replace the VC-137 in service. Also the original 757 prototype is being retrofitted with a 'wing' section and a nosecone off an F-22 to test they radar antennas for that aircraft.
B-767 There are no US military versions if this aircraft yet. But Boeing is activly marketing it as the next generation of military airframe since the 707 fuselage is out of production. Four AWACS aircraft have been built for Japan. and Boeing is market versions for air-refueling and other missions.
I hope this helps
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.