I agree with Spiceycat that there isn't one. The Downtown Disney hotels that are considered walking distance to DTD are still a good 3/4 of a mile away. Plus they are far from all the theme parks.
My recommendation would be to stay at a Value Resort, where you can take a bus to and from all the parks as well as Downtown Disney. Plus, the pool bar at All Star Movies ( a Value Resort) was really hopping when we were at the resort last Saturday night--it seemed like a fun place.
If you stay at any resort, you can also get a bus to and from Epcot, where you can drink to your heart's content. If you choose, after Epcot you can walk over to the Swan/Dolphin (deluxe resorts just outside of Epcot), catch a bus to Pleasure Island/Downtown Disney, visit some clubs at DTD, then catch a bus from DTD back to your Value Resort.
The Disney bus transportation to/from the resorts and parks is absolutely wonderful.