Depending on how long you are there and where you are staying/visiting, here are a few suggestions (btw, I agree you should check out the Cherry Blossoms!)
Georgetown– I disagree about CakeLove (sorry ChelseaMorning). If you have a sweet tooth Georgetown cupcake is the place to be! Yum! The line can go up the block but that’s only cause there is just enough room for about 4 people inside the cupcakerie. Georgetown also has a lot of good shopping. If you are looking for nightlife, Garrett’s has a good HH and yummy burgers. Mr Smiths is cool but can get pretty crowded. If you love brunch like I do, then check out Chadwicks on K Street (theres another in Alexandria I think) … the food there is pretty good and they have a nice brunch special. Also walk by the canal if you can, it’s pretty neat, especially when they have the boat out!
Foggy Bottom — It’s mostly GWU campus but its a nice place to take a stroll and see some pretty homes and flowers. Froggy Bottom Pub has decent pizza for a cheap eat!
Museums, etx — I’m a fan of the Smithsonian (its free!) The National Gallery has some great pieces but the Museum of Natural History is actually pretty neat also. The American History Museum (think, Kermit the Frog, Dorothy’s Ruby Slippers, Jerry Seinfeld’s Puffy Shirt) is very cool. I have to get to the Portrait Gallery but that is supposed to be pretty cool. If you are looking for a place to eat around here, I say hop on the metro or take a stroll up 7th to Matchbox (http://www.matchboxdc.com) in China Town. I recommend the fire and smoke pizza with buffalo mozz!
If you get the chance to stroll into Old Town (Alexandria, VA) take a walk down by the water front. So beautiful! King Street is a nice place to explore.
If you are driving, go to Bob and Edith’s Diner in Arlington, VA (on Columbia Pike), cheap diner food that doesn’t make you sick to your stomach!
There are so many good restaurants! I love Filomena in Georgetown for Italian, Founding Farmers (http://www.wearefoundingfarmers.com), Firefly (great atmosphere!), Bangkok 54 in Arlington, VA for Thai (Cheap Eat!) and you can’t go wrong with Clyde’s (get the crab cakes!)
jkoala — i LOVE your friendly reminder about the metro, Please stay to the right!
As you can tell, I love food!