Liberty Travel
We booked a vacation to the Riviera Maya in the Yucatan through Liberty Travel, and if you're interested in hassle free planning to a resort where everything is taken care of, Liberty Travel does a great job. They specialize in these types of trips and they do it well (relatively affordably from what we reserached). That being said, be careful that the all-inclusive resort is what you're looking for. While Liberty Travel did an excellent job and we had a great time, I don't know that we'd necessarily do another all-inclusive trip again. If you're in to cruise ships, you'll be in to all-inclusives, and Liberty Travel is a great way to go.
Gandel's Liquors
While this might not be the liquor store lunch everyone might have in mind, I would recommend stopping in to Gandel's liquor store and trying out their deli. The sandwiches aren't the healthiest, but they're good when you need something quick, they're big, they're affordable, and they're actually decent. At lunchtime, expect a sizable crowd of monkeys from the Hill waiting for their order to be called up.
Cake Love Llc
Whether you need to pick up a birthday cake, a cake for a dinner party, or you just want cake, Cake Love is the place to go. It's been written up many times in teh Washington Post if you want more information, but everyone I know would recommend their desserts. The store's website used to leave something to be desired, but I just checked (www.cakelove.com) and it looks like they've finally revamped it, with pictures, prices, and other information.
Meeps & Aunt Neensies Vintage Clothing
Check out Meeps on U Street. They've got a decent selection of mens clothing - from shoes to jackets to retro shirts to pants. The prices might be a little high, but then again the selection is probably worth it. It definitely beats sifting through the piles at the Salvation Army in hopes of finding something; Meeps has already separated out the vintage items.
Home Rule
For the city dweller in Washington that's looking for ways to spruce up their apartment or condo, check out Home Rule on 14th Street. It's small, but it's everything you need in terms of interested bathroom and kitchen related supplies, and it's not your run of the mill stuff. While you're there, there are a ton of other new businesses opening up on 14th Street that will likely cover all of your housing needs...a hardware store, plant store, furniture, clothing, whatever else you might need.
Go Mama Go
This place has some of the most interesting items you'll ever find for the home. The goods come from all over the world, and all are of high quality. It's great for someone living in DC that's looking to spruce up their apartment, but it's also worth checking out if you're in DC on vacation and are looking for interesting things for the home. Everything from lamps to dinnerware to tables to candles to cards. The owner has clearly done his / her homework.
Cardella Construction Company
If you live in or around the DC area and you're looking for a quality wine shop, MacArthur Liquor is the place to go. Their selection is unsurpassed, and their prices are reasonable. The staff there is also extremely knowledgeable and more than happy to help. Unlike most local win shops, their website is also fairly informative (presumably because they do a fair amount of mail order business). It's also located next door to a great pizza restaurant.
Friendship Flower Shop
Friendship Flower Shop does a decent job with orders (for either pickup or delivery) and they also have a decent flower selection. The only drawback I've found is that when you go in there you feel like you're interrupting the staff, which is busy making floral arrangements. But if you can get around that, they usually have a decent selection of quality flowers, some plants, etc.
Old Town Trolley Tours of Washington
If you have out-of-town guests visiting you in DC, be sure to have them take the Old Town Trolley tour. The trolleys have pickup spots all over DC, and you can hop on and hop off at every place. The trolley takes you through great areas of the city - the Mall, Embassy Row, the National Cathedral, the zoo. Plus, you can send your guests out for the day and know they'll be taken care of in case you can't check out the sights with them.
Daro Realty Inc
I've lived in Washington for 8 years and am on my third landlord. It may simply be because I'm living in a nicer building now than when I first moved here, but so far, Daro has been an excellent landlord. The building is clean and well cared for, they regularly schedule visits from pest control rather than waiting for complaints, and if you put in a maintenance request (whether small or large) the request is usually filled within 24 hours. I might just have good staff working in my building, but I'm assuming it comes from the top.