Gettysburg Battlefield area is just amazing! Driving through the areas where the civil war was fought gives you a real sense of what the battle was all about. The museums, tour and stories told by some of the "characters" on the site are so educational and informative. I recommend, at the very least, buying a tour tape in the Cyclorama, if you can't get a live guide. There's so much to see that you will spend at least a full day at the battlefield. This being a National Park, driving around the battlefield is free. There is no admission! A great family destination for a road trip vacation.
This museum is AWESOME! It has a vast dispaly of aircraft and space vehicles. It houses the Wright Brother's plane, The Spirit of St Louis and other airplane "firsts", as well as space modules like Apollo 11. There's a lot to see and you can spend several hours going through the place. One of the best things about bringing the whole family to the Air and Space Museum, besides the history lessons, is that it is FREE!
Essex Steam Train and Riverboat is a very cool place to visit if you're into old trains. There are many antique passanger cars and a train club has a huge model train set-up inside one of the buildings. They also sponsor events like Day out with Thomas, Polar Express and The Santa Special. My suggestion is to schedule your tickets for very early if you're doing one of the events. The place fills up pretty quickly by mid-morning, but if you're one of the first ones there, you get a few hours to see everything before the crowd. They also have dinner trains and riverboat cruises scheduled out of their station. Check out their website!
This is one of the great places in the DC area to visit that is FREE! The zoo is part of the Smithsonian Institute, but is not located downtown near the museums. Because it is a National Zoo, admission is free. You can spend an afternoon walking around the grounds. Don't miss the Panda exhibit with little Tai Shan!
The DCU Center (formerly called The Worcester Centrum) is a bit smaller than your average arena, but it has everything you'd need. There are concessions and ATM's inside. It is one of the easiest places to get to. There is a parking garage for the center, but during big events, a few other local parking lots open up and charge to park there.
The Dunkin Donuts Center is a great venue to see shows. Whether it's the circus or a concert, this is the easiest place to get in and out of, and the seating is great. There is a parking garage right next to it, so it's not a long walk at all. There are consessions and ATM's inside.
State of the Arts is a great place for kids to learn the art of Karate. The teachers are nice, but thorough. They work the kids up to each belt, and take special care to show them technique. Many student's parents also take karate lessons here. It is a great place to become involved in the sport.
John's Reconditioning does an excellent job power washing the exterior of your home. They come in with their truck, and use pressurized water to clean the dirt and filth off the aging paint on your home. If you'd like to repaint, but can't do it right away, John's Reconditioning may give your current paint some extra life.
JustStrings is your one-stop shopping place for anything that has to do with musical instrument strings. Whatever obscure musical instrument you may need strings for, they will find it. They carry all gauges and types of instrument strings. They have a vast array of guitar and violin strings, which you can buy either by the set, or just a replacement string. Their store front is understated, but they will have what you need. If by chance they don't have it, they will get it to you faster than anyone else.
This is a HUGE shopping area. Every store imaginable, and some that aren't, are here. You should get there early, because the ample parking lot still fills up quickly. There are stores for clothing, shoes, electronics, books, childrens clothing, glasses, dishes/china, kitchen gadgets and much, much more. There are a couple of candy stores, a hair place and a fudge shop too. There are a few restaurants around the outlet too. It gets crazy around the holidays, so heed my warning and go early!