If you're going to be anywhere near Foggy Bottom, Georgetown Tobacconist has pipes, tins, store blends, and a great staff. Though there is no "Lounge", you can smoke in there.
If you'll be downtown, closer to the capitol, there's the historic W Curtis Draper's - Americas third oldest tobacconist (behind Iwan Reis and LJ Peretti). Decent selection of pipes, tins, and bulk tobaccos. Despite the comfy chairs scattered about, you can not smoke in there.
There are a few others in the city and suburbs on both the Maryland and Virginia sides, tho they are mostly cigar lounges. Some will have pipe stuff, some won't.
I'll also take this opportunity to mention the
retail directory on this very site. We are all able to post store info and reviews to help each other out when planning visits.