new to capital hill
First things first, if you're going to live here, you should know that it's "Capitol" not "Capital". I wouldn't correct you if you were a tourist...
Now that the spelling lesson is over, good restaurants not mentioned are White Tiger for Indian on Mass Ave, Ugly Mug has some good bar food on 8th St. If you have a morning/early afternoon hankering for breakfast, Pete's Diner, next to Le Bon Cafe works pretty well.
For high end - Charlie Palmer's, excellent food. Also if you like seeing famous people, or at least pictures of famous people, try Monocle.
I really like Pete's Diner for pretty cheap, good breakfast food.
I did not have such a good experience at Le Bon Cafe the 2 times that I went, so I'm recommending against here. Once, the bread on my sandwich was so hard, I could only eat the meat part (that was tasty, though); and the second time I had my son along in his car seat, and they weren't helpful at all service-wise. I know it's a cafe, so service isn't so expected, but...I didn't expect looks either.
Anyway, Tortilla Coast is good for its happy hours (a lot of the Hill folks go there) and its chips & salsa (plus drinks). The food is just so-so, but great in a pinch. Great place for meeting people during its happy hours too.
Around the corner from T-Coast (as it's affectionately known) is a decent Thai place whose name I can't recall right now.
I second recs. to Sonoma and Charlie Palmer's. But I would *avoid* Chinese options around there -- I haven't found any I liked when I worked near there.
I also recommend dining in Congress -- Longworth cafeteria has a wide variety to choose from that isn't so bad for lunch on the weekdays, if you can swing it.
For something healthy, I really enjoyed my sandwiches and smoothies from the Wellness Cafe. It is a bit pricey, but delish.
325 Pennsylvania Ave SE, Washington, DC
Explore H Street, NE. Best fried fish in the city at Horace and Dickie's - carry out only. Two great coffee house - Sidamo Ethiopian Coffee and SOVA with free wifi. Granville Moore's excellent mussels, burgers and frites and wide range of Belgian brews. The Argonaut just changed its menu to more local and seasonal foods without budget-busting prices plus widened its range of beers to some really interesting choices. The Palace of Wonders is in a class of its own - the freak show and burlesque doesn't save the pedestrian food. Rock and Roll Hotel offers amazing indie bands and bar food. Napa 1015 has Happy Hour specials and a full menu that's getting high praise, although I haven't hit it yet.
The frozen tropics blog keeps everyone up to date on what's happening. There's a list of the restaurants with addresses and hours. http://frozentropics.blogspot.com/
Locanda is a promising modern Italian place - upscale pricing but not exorbitant. If you're jonesing for Peruvian/Mexican, Las Placitas isn't too bad. I like to have a drink at Mr. Henry's. And Tunnicliffs has tasty pub fare. Have a drink at Banana Cafe but skip the food. Sonoma is good for cheese/pasta/wine but I find the service to be a huge detriment. And for private, guilty pleasures...there's Popeyes. Just don't go there during lunch or everyone in your office will know EXACTLY where you've been by that distinctive grease smell.