So, I LOVE Washington DC! I'll be spending five days there in a few weeks, and I'm looking for things I haven't seen/done yet. What are some of your favorite, smaller, less seen monuments, buildings, museums, etc
Out of the major monuments/buildings, the only one I haven't visited is the National Cathedral and that's on the list.
Also, any walking tours you've loved? (Particularly goofy ones like "The Darker Side of DC", etc.)
I'll be using public transport the whole time, so venturing far off won't be an option, but I don't mind a good walk!

You've been to the FDR. You've been to the Korea...at NIGHT.

You've been to the Renwick. You've been to the National Building Museum. You've been to Ford's. The Spy. The Folger Library. Congressional Cemetery. Dunbarton Oaks. Hillwood.

National Shrine. AFIP Medical Museum

In no particular order:

Folger Shakespeare Library
Library of Congress
Dumbarton Oaks
Hillwood Estate
Lunch or Dinner at an Ethiopian restaurant
Meridian Hill Park
Eastern Market on the weekends
Baseball game
National Building Museum
National Museum of Women in the Arts
Postal Museum
African Art Museum
Freer Asian Art Museum
Phillips Collection
Exocist Steps Georgetown
Lincoln's Summer Cottage
Paddle Boats on the Tidal Basin
Roosevelt Island
National Botanical Gardens
Embassy Tours
Navy Museum
Octagon House
Frederick Douglass National Historic Sight
Old Town Alexandria

Anderson House near DuPont Circle . Our hotel was nearby and I had some time to kill, so I took a docent tour. So interesting and I loved it.

http://www.societyofthecincinnati.org/visit/tours

Add the National Arboretum and the American Indian Museum to that list.

Udvar-Hazy air and Spaced center

http://airandspace.si.edu/visit/udvar-hazy-center/

Udvar-Hazy is part of the Smithsonian complex and the lesser known cousin of the Air and Space museum on the mall. Although it's rather tedious to get to using public transportation, it's well worth it~no hordes of school children and an impressive collection of planes. My nephew loved seeing the SR-71 and the space shuttle, and I was awed by the Concorde.

Another recommendation would be the National Museum of Crime and Punishment. I went only because DD (a criminal justice major) wanted to go, but I found it fascinating. www.crimemuseum.org

Although not in DC, the Stabler-Leadbeater Apothecary Museum in Alexandria is interesting. Take Metro to Alexandria, and use the trolley. www.apothecarymuseum.org/

Something else worth a look is the National Law Enforcement Memorial. One the walls are etched the names of law enforcement officers who have died in the line of duty.

www.nleomf.com

obxgirl's list is terrific!!

And yet I thought of an addition: Tudor Place, near Dumbarton Oaks.
https://www.tudorplace.org

Second Dumbarton Oaks and the Navy Museum.

Woodrow Wilson house.

Take a Segway tour! I used Capital Segway but there are several companies that do this.

Have you been to the Museum of the American Indian? It's an interesting spot and the cafeteria, Mitsitam, is fantastic.

I also enjoy the Corcoran (recently absorbed by NGA) and the Phillips Collection.

There are two Dumbartons, Dumbartons Oaks and Dumbarton House. Both are in Georgetown and both are worth a visit.

I like obxgirl's list! A couple of things not yet mentioned:
The visitor center of the US Forest Service is a red brick building in the midst of all those marble buildings.
It not far east of the Washington Monument. Sometimes they have Smokey Bear outside the door. Inside you can see Smokey's office.
North of the Washington Monument is the Ellipse. At the north end of the Ellipse is the Zero Milestone. From this spot you have a great view of the south side of the White House.

The monument's at night. Just beautiful.

>AFIP Medical Museum<

This, too, is a bit of a jaunt via Metro and about a 20 minute walk from the Metro station..........it's not a huge museum, but it's very interesting.

On our last trip to DC, we finally made it to the Museum of the American Indian. It had been a long time since we'd been in DC purely on a sightseeing trip - our usual trips to DC are for work with sightseeing here and there in our free time - but we knew that we would want to spend a lot of time in the American Indian Museum. We spent hours and hours there. I think it is a definite must-see.

We also saw the Woodrow Wilson house on that trip, which I found to be fascinating.

The Phillips Collection is another great museum that people tend to miss. And it isn't far from the WW house, so you could visit them together

We just returned from DC. We took a Happy Hour cruise on the Potomac. It left from the Georgetown waterfront. It started at 6:15 and lasted 90 minutes. The sun was out when we set sail and it was dark when we returned so the view was beautiful.

The National Zoo is also very nice. The first time we went we went in to see the pandas and left. This time we saw the whole zoo. It is really very nice. Just be aware that it is all downhill going in so the walk out may be a challenge.