Alex and I discovered Best of Thai Noodle (map, reviews) right down the street from my flat. I've lived three blocks away for four years and I never went in. I'm glad I finally did. The soups are really yummy and they're all six or seven bucks. In fact, I think everything on their menu is six or seven bucks.
We usually get the won ton soup and the duck soup (yeah, together, two soups. So what? they're Suuuuper yummy! )