Check out Code 10 on Washington Street for a great hot dog! i am a purist, so I cannot vouch for the chili dogs, or cheese dogs, or other such concoction, but for the good old (steamed)American staple, they do a great job.
They have Pearl, Hebrew National, Rhode Island Reds (previously unknown to me, and definitely the best of the bunch), Turkey Dogs, and Tofu Pups (which are a great non meat alternative for those of us with a vegan in the family).
If you want a realy treat, walk across Washington Street to Flour for dessert. They are fantastic, especially their Oatmeal Raisin Cookies.