On my first trip to Washington, DC, I was merely flying in/out of the area and driving into Virginia for work. However, I had a about 1/2 day where I could attempt to go sightseeing. Obviously, half a day is woefully insufficient for DC. Still, I had a cousin-in-law that lived/worked there and she suggested the Capital Segway tour. I felt a little awkward doing it "alone" but it was absolutely fabulous. I took the last tour of the evening and it was perfect. There's no other way to see that many sites and monuments from that vantage point, and the segways were a blast and easy to operate. If you only have a few hours and want to get the most bang for your $$ - this is it. The guides are also very knowledgeable and make it a fun and informative tour.

I have since been back to Washington DC several times and been able to actually tour many of the Smithsonians, the Capitol, and other key monuments/sites but the Segway tour is still top on my list. I have done it more than once and can't wait until our sons are old enough to operate the Segways as well (age minimum is 16)

I also enjoyed the Old Time Trolley tour - and would highly recommend it too, but you should take it when you have time to actually get on/off and visit the sites that it takes you to.