First, to avoid definitional problems, I'm willing to include anything that has some sort of broth and is eaten from a bowl, whether as an entree (pho, menudo, cioppino) or as a separate course. If it's served in a bowl, but transfered to a plate before eating, or if it doesn't have something liquid enough to count as broth, then it's a stew, and doesn't count. Chili counts, no matter how thick it may be. Other than that, consider the field wide open to all styles and ethnic origins.
Also, given that this thread may become one that will be found in the future by people searching for a general guide to the best available, rather than a commentary on any one soup at any one place, try to put the geographic location of your nomination toward the front of your post, such as "Baltimore - the Fish Tea at Ras Doobie's..." followed by your description of the dish itself, why you like it, or whatever else you're going to say.
Sweet and Spicy Salmon soup at Nam Viet. I always get the cup size as my appetizer there. Nice clear broth that's slightly sweet from tomato and pineapple (usually pineapple for me is a deal breaker), with nice chunks of salmon and topped with sprouts, cilantro, maybe a couple of other things. Incredible!
ANY soup at Corduroy. Tom Power is a freakin genius when it comes to soup. I've never had a broth there that was anything short of fantastic.
Baltimore- I love the lentil soup at Samos (but the soup choices differ daily, it's frequently there, but not always) other choices are nothing special
Also, remember having a great cream of crab at Birches a few times, but a few years ago
Oh-- forgot to mention all the soups from the stand in Belvedere Square Market- (forget what it's really called now)
Cream of chestnut soup at Montmartre.
Chilled chervil soup at Restaurant Eve.
Homemade turkey noodle at The Royal.