If you have not heard about them yet, online coupon websites are a huge hit. I've noticed some interesting half-price offers for the Washington, D.C. area for both residents and visitors. Today's Groupon is a D.C. Tourmobile sightseeing coupon for just $7. If you're not a member of either Groupon or Living Social, signing up is free and each day you get an email for daily deals in your area. You can also look at deals in other cities you plan to visit for 50% off coupons for restaurants, museums and activities. Building Collectors might want to sign up for both and keep watch on the deals in DC especially if you plan to extend your visit to see more of our nation's capital.