Conference will bring me to Washington DC at the end of this month. Flying in to R. Reagan on Friday and staying at the Omni. Will have time on Friday, Sat. and Sunday to wander around. Not much after that.
I won't have wheels, so I'm looking at where I can get via cab or public transportation.
I am pretty sure I want to get to the Smithsonian Air and Space Museum. Any other must-do's??
The Vietnam Wall. Any of the other monuments on the Mall you can get to. the main Smithsonian, also on the Mall.
Tomb of the unknown soldier - Arlington Nat Cemetery. We did a mint tour once and the FBI building tour was sweet but was 4 hours long.
Look on the back of an old penny and head over to see if it matches Lincoln Memorial.
Last time I went a week wasn't enough time
You don't want wheels - good walking shoes.
most everything in DC is availible via mass transit or Cab. It is pretty well set up for sightseerers
Stay off mass transit. Just do unless you're broke. You literally can walk quicker oft times. If you go to Arlington try to catch a full military funeral. Last year an older acquaintance got the full deal. Very impressive especially for a European. Capitals game if you're a die hard hockey fan, they've got a loyal fan base. Pretty sure the Nationals will be done by the end of the week never mind the month. The monuments at night are actually quite nice, better if you had your main squeeze probably. If you're a walker and have the time stroll down Connecticut from the Omni to the White House, Mall etc. just to get a fairly good feel of the city and its denizens. There are bike share thingies just randomly seemingly abandoned on the sidewalk or at stations which can cut time from one place to the other. The Marine Corps band plays Fridays throughout most of the year and there is presenting of colors at the Navy memorial I think which is across from Archives with the Constitution on view. Maybe the ice rink at the Sculpture Garden will up and running. There's lots to do. Remember any museum will chew up a bunch of your time unexpectedly in a good way. 
Museums. They are all excellent, and don’t charge admission; a nice feature on a business trip when you’re traveling to make money rather than spend it. Going to museums solo is also nice in that you can go at your own pace.
The holocoast museum is very thorough. I spent at least 4 hours there but only made it about halfway through the displays.
You aren't in the financial crimes industry are you? I'll be in DC the 23-27th or something around there for a conference and I'm in the same boat. I've been several times but it's been a little while and this time I'll also be without a car.
In reply to crankwalk :
Nope - I work in Facilities at an Educational institution .
If you're comfortable around traffic on a bicycle, I would highly recommend using Capital Bikeshare. It'll get you around faster than mass transit and a cab, and will allow you to get to more things.
The International Spy Museum is neat. It charges admission, but I think it's well worth a couple of hours if you can get a discounted ticket.
There's a catacomb under Dupont Circle that uses to be a mall of sorts. Walk through Georgetown and decide on a spot to dine. Also try Edy's peruvian chicken in Falls Church, 
get yucca, because fries are for suckers.
Also Hit up Victor's Grill in Falls Church
because meat sweats are so amazingly worth it.
again, plantains and yucca are recommended as sides as well.
If you've got time I would recommend the Old Town Trolley Co. They cruise around the whole district and make stops at most of the places you would want to see on a quick trip. We used it as a taxi service, your ticket is good for two days with on and off service. Like others have said, Arlington is a must see as well as the Vietnam Wall and Lincoln Memorial along with Smithsonian, they are all free. Treasury was cool and the Halocaust museum is very good, but it's heavy. Having worked in Bethesda for 2 years, when the wife and kids would come up we would hit all of the museums, so we have seen most of them. I would recommend Uber/Lyft, I have had good experiences with them getting around in "foreign" lands.
The Smithsonian Air and Space, and Museum of Natural History. That is two days right there.
Make sure you see both Air and Space Musems. Udvar-Hazy is pretty impressive and has different offerings than the one downtown.
Other than that:
If you're there on Sunday 10/22, the Marine Corps Marathon will have a lot of streets closed around the monuments and museums.
Udvar-Hazy is going to be difficult on public transport, but certainly worth the trip. I'd probably rent a car for that.
Check out the Elephant and Castle pub at 12th and Pennsylvania Ave. Get the Slum Dog - you're welcome in advance.
The Mall is really nice after dark. We walked around until about 11-12 when we were there.
I didn't think of the Tomb of the Unknown Soldier in my first post, that is a must see if you have time.
It's been years since I was last in Washington, but I thought the Metrorail system worked pretty well for getting around town - depending on where you will be staying, it's worth checking out.
Arlington Cemmetary is sobering and the changing of the guard is impressive. Lincoln memorial, WWII memorial and others are something to see.
Dates of travel are October 27-November 1.
Another vote for visiting the Udvar-Hazy National Air&Space if you have the time. It's accessible via public transit but you'll have to take the Silver Line out to Reston and then pick up a bus from there. 90 minutes each way is a bit steep but worth it if you're into air/space craft.
https://airandspace.si.edu/udvar-hazy-center
In reply to Armitage :
Gotta get there - just to see the Blackbird and the Shuttle.
My brother said the spy museum was cool.
I highly recommend the Udvar-Hazey if you can get down there. Mrs. DX and I were there this past May and it was incredible. She probably stood and drooled at the space shuttle for a good 10 minutes. Very easy to spend a whole day there. There is an observation tower where you can watch planes take off from Dulles since it is only a couple miles away..
More in DC proper, The WW2 Memorial is worth seeing. Also, Mrs. DX took some of her college students on a trip to the African American History Museum (I tagged along) and it was very impressive to say the least. Easy to spend a few hours in there. The cafe in the museum has some of the best fried chicken I've ever had also. The White House is interesting to walk in the front/back of. It is very small looking in person compared to what it looks like on tv. I highly recommend eating at a chicken place named Nandos Peri Peri https://www.nandosperiperi.com/eat/restaurants/18th-street
It is a Porteguese Chicken Restaurant and there are only a couple in the US and DC has two of them. They make really good chicken livers and good beer as well.
In reply to dxman92 :
There are no fewer than 8 Nando's in Maryland now, they've begun franchising.
I went to the Steven Udvar-Hazy museum before it was in its current state. The Shuttle they had at that time was only a glider version. I figured they would get the real deal once they were retired. Being an old airport rat growing up, I was like a little kid again. I would give a kidney to get inside the Silverhill buildings.
You'll need to log in to post.
