I've been reading lately about the new nuclear thermal engines that have been developed in the last 10 years or so. They have a specific impulse of around 980, and can be made to produce a thrust of around 14kN. Best of all, they only mass a few hundred kg, including the reactor housing and control systems. Google "MITEE nuclear engine" for cool details. With something like that, could you build a ship that's carried up in the shuttle, launched with a crew to the moon, lands, and then returns to low earth orbit?
The shuttle has a cargo capacity of about 24 tons. You need a velocity change of about 11km/sec to go from LEO to the moon's surface and back. With the kind of high specific impulse that these engines provide, you would only need a mass ratio of around 3.7, so our ship could be 7.5 tons empty and 24 tons full of fuel. You would only need two engines to lift off from the moon, but assume three so that you have a backup if one fails. All three together would probably be less than 1 ton. You would also need fuel tanks for your 16.5 tons of fuel, so call that another 1.5 tons. This leaves you with about 5 tons for the rest of the ship+crew+cargo. Not a lot, but the empty LEM from the Apollo missions was only something like 4.5 tons empty, and that included the mass of the engines and fuel tanks, so it seems doable. As a bonus, the engines can also provide electrical power during the flight.
It could be launched from the space shuttle and sent to the moon and back. The crew would need to transfer to some sort of earth-return vehicle for the trip back, probably by docking with the ISS. The ship stays in LEO, and if you want to make another trip you just send up another shuttle with 16.5 tons of fuel and some new crew, gas the thing back up, and make the trip again. You could imagine it being cycled with each shuttle trip bringing up a new crew+fuel and picking up the crew from the previous mission to bring them back to earth.