Washington DC USA – Things To Do and See

You probably already have an idea of things you want to do on your next visit to Washington DC, but like a lot of people maybe you don’t have enough activities to fill up all your days, or maybe you have the opposite problem.  Maybe you are visiting Washington DC for only a 3 full days and you have too many ideas of things to see and you want to narrow them down a little bit.  So what sites should you visit if you are there only a few days?  Or what is a long list of places that are worth seeing if I’m in DC for a week or more?