I like Celadon (in DC) and Elizabeth Arden Red Door (in Arlington, right next to a good shopping mall, Pentagon City).
For super indulgence, there's a spa at the Ritz Carlton Georgetown - you can valet park there for free then go shopping before or after. I've heard there are other good spas in G'town, but I haven't been to any besides the Ritz.
for shopping however, I like going to the little shops on U Street and Adam Morgan. G'town also has some nice shops but the place tends to get overly crowded.
Now if you really want a bunch of shops in a concentrated area you have to hit up Tyson's Corner..
the mall there is HUGE and between the Tyson's I and II you can probably spend all day shopping..