There's a "new" hot truck outside One State Street Plaza at the corner of Whitehall and Water Streets (near the S.I. Ferry station for those unfamiliar with the area). I say "new", because the guy who owns it used to have a breakfast-only, no hot-foods cart, with the best bagels in the area (not saying much, I know).
In the last 10 days, in addition to my morning bagel, I've had his hamburger platter (with iceberg lettuce, two slices of a beefsteak tomato, french fries and a "Mr. Pickle" pickle) and today his lunch special of lemon fried fillet of sole (with the same sides as above, plus a lemon). Both main dishes were surprisingly good. The burgers are clearly handmade (sign says 100% fresh ground sirloin, and you can tell by the shape that they're not preprocessed) and good taste. The sole today was fresh from the Fulton Street market; I had two breaded pieces, fairly thick. The breading was crispy, but not too thick, leaving the fish nicely moist and definitely fresh-tasting.
The fries were standard i.e. nothing special, about a third-of-an-inch thick. The pickles were great. I think the burger platter cost $3.50 (will check on Monday) and the lemon sole special was $7.50 ($5.25 for just the sole).
He's got a bunch of other things too, which I'll be checking out over the next few weeks. People in the area should check it out as a lunchtime option.