Well, wasn't this just a handy thread! I will be heading for DC myself in another week and a half, and will also be staying in Crystal City, though at the Hyatt instead of the Marriott. All of this information has been so helpful!
I do have a couple of questions, though...I will have about 6 to 8 hours on Tuesday to cram in as much sightseeing as possible. Is my best bet to hop the Metro and head to the National Mall? Or are there other not to be missed sites? I was thinking I might start at the Smithsonian Castle, but then what? Head for the Capitol? The White House? The Library of Congress? I'm pretty open to ideas for making the most of my one totally free day! Oh, and any must try restaurants?
Also, does the Metro sell anything like a one or two day pass? If so, would those be the best options? I for sure have Tuesday open, but not sure about Wednesday...I probably have some time in the evening, but that would be about it. Heading back on Thursday.
At any rate, I am totally looking forward to trying out my brand new Aeronaut and Co-pilot, which should arrive this Tuesday, giving me a week to test pack. I know -- the Aeronaut is probably overkill for such a short trip, but I've been wanting one for EVER, and since I suddenly find that I will be making several trips over the next few months for work, I thought this would be a good justification to finally bite the bullet and order one. Between the Aeronaut and the Co-Pilot, I am looking forward to no-checked-baggage Nirvana!
I would suggest planning out what you want to see as much as possible. 6-8 hours is not much time in D.C. as there is so much to see. The metro does sell all day passes Metro - Home page and just a reminder, in case it hasn't already been stated -- the metro in D.C. is crowded at any time but jammed to the gills during the commuting hours in the a.m. and p.m. during work days. If possible try to avoid those times. Also, you have to pay to get out of a metro station. It is an odd set up. We go up there to see concerts a lot and had to make a couple of different train changes to get to the Verizon Center. We accidentally went out of one station within the herd of people we were in and had to pay to get out at the end of the night as our card ran out of money. (Also, the metro does not run 24/7 and is an old infrastructure in need of some serious updating -- a well known problem that no one wants to pay for up there). The Washington Monument is still closed from the earthquake. It won't be open again until 2014 I believe. The museums are great and I quite enjoyed the National Archives which is also a relatively quick trip if you can fit it in. I've lived 2 hours from D.C. my entire life and still haven't really seen everything up there. (Traffic is a nightmare and it is very expensive so admittedly we don't go often). I don't think I've eaten at a bad restaurant there either - so pick what you like!
Oh and don't forget the camera!
p.s. Forgot to mention -- lots of walking. Expect a lot of walking :)
Thanks for the travel tips, Photocat -- particularly about using the Metro! I believe I will miss the morning commute, but may hit the evening one. At least I've been forewarned! And I've got my comfortable walking shoes ready to go!
Sacharissa, you might want to look at historygal's Mr. Synapse Goes to Wahington thread. (Her meeting was in Bethesda, MD, so she was staying just outside the north tip of DC, while Crystal City, VA is at the southern end – close to National Airport and just across the river from the National Mall, etc. The National Mall area is separate from most of the other places you'd go to, and I think the easiest way to get there is to take the Metro, then walk to the Smithsonian and other sights along there. For other parts of DC, you might find the DC Circulator bus routes more convenient than learning the Metro bus routes and subway stops. There's a link to their web site (that I just fixed so it will work as a link) in my post to Janine about ways to get to Georgetown, and there are maps of their different routes. They also have discount 1-day and 3-day passes.
Your hotel (Hyatt) is further from the Crystal City Metro stop than Janine's (Marriott) or than the Crystal City hotel I last stayed at (Hilton). They run a shuttle bus to the Crystal City metro stop, and I think it only runs up through a certain time in the evening. You might find TripAdvisor's web site handy for things to do in DC and their 3 Days in Washington, DC page. Also, the Washington Post put out a free Explore D.C. iPhone app that can be handy, if you have an iOS device.
I like the Newseum as somewhere that gets relatively less coverage as a tourist site, but it isn't somewhere I'd include if you're pressed for time. Also, this has paid admission (although the Explore D.C. app Deals section will get you a $5 discount through 11/9/12).
HTH. It's been a while since I lived in DC, so others may have better suggestions. I'm disheartened by number of bookstores that have closed there in recent (or not-so-recent) years.