Looking for good b-fast places in fun area of DC for out of town guests??
Weekday or weekend? This is a big brunch town. Leopold's Kafe in Georgetown has great Austrian/German fare and is in a beautiful little spot between the Canal and M Street. If you're going to be around the National Mall on a weekday, Teaism, just above the Navy Memorial is one of the only interesting places nearby. The Tabard Inn near Dupont Circle has a great brunch (homemade donuts) and of course, there's the Blue Duck Tavern. Go to there website- it's as good (and expensive) as it seems.
I 2nd Leopold's Cafe. It isg ood (tho gets very busy if you don't get there early). In Arlington (Shirlington specifically), Carlyle Grand is an all time favorite. Also in Arlington (Clarendon) Boulevard Woodgrill is very good.
I've had good experiences at the Silver Dinner in Clarendon (about one block up from the metro). It can get crowded, but the line moves very fast. Service is efficient and pleasant and the food is really good- classic diner food, nothing fancy but they've never once screwed up my eggs benedict. It's cheap and fast, not ideal for a linger-y mimosa brunch, but good for breakfast.
Let us know if you're looking for something more adventurous, there are some different suggestions I'd give for brunch in DC proper (mainly Cafe Atlantico or the garden/courtyard at Poste).
In Falls Church, there's the Original Pancake House. I've heard it exists elsewhere, but really, it's the best traditional breakfast place I've been to in the DC metro area. I heartily disagree with other posters that Silver Diner (or any other diner) in the area is worth your time. I've found the food bland and eggs overcooked everywhere else.
If you want something savory for breakfast, there's China Garden in Rosslyn (in the ABC building @ Lynn and Wilson) which has a pretty good dim sum brunch on weekends.
The best mimosa brunch I've attended was at Perry's in Adams Morgan. It's a Drag Brunch, so the entertainment outshines the food. Or is that out-sparkles? (Yes, drag as in drag queens.) It's a ton of fun with the right crowd. Just remember to take some $ingle$ and be prepared to marvel at the possibilities of plastic surgery.
Firefly in Dupont has $1 mimosas. I've been there a few times and always enjoyed their brunch.
cafe atlantico dim sum brunch is also great