The list of leguminous tree species (members of the Fabaceae family) I've encountered is short. I've seen Kentucky Yellow-wood (Cladrastis kentukea), Redbud (Cercis canadensis), Silk-tree (Albizia julibrissin), and Honey-locust (Gleditsia triacanthos), but for the most part they've been ornamental plantings found along roadsides or near homes. The notable exception is Black Locust (Robinia pseudoacacia), a species who while not native to New England has naturalized in a variety of disturbed habitats throughout the region.
In winter, Black Locust trees can be recognized by their persisting pods, which split open to reveal small dark seeds. Bark and twig characteristics are also useful. Branches often have pairs of sharp spines at each leaf node. Winter buds are mostly hidden, sometimes peeking out from under leaf scars. Small trees can be decorated with formidable thorns. Black Locust bark develops deep ridges with age. (To view the following photos in full-size, click here.)
Black Locust can grow quickly, even in poor soils, and has wood that is rot-resistant and energy dense. These features, along with an ability to re-sprout after being cut, make this species a valuable renewable building material and firewood source.
The edible flowers are worth seeking out in spring (see Foraging Wild Flowers: Black Locust), and Haines reports that immature pods and mature seeds (removed from their pods) are edible when cooked. (He notes that mature seeds should be soaked prior to cooking to deactivate antinutrients -- read pages 59-60 of Ancestral Plants for more details). For more uses of Black Locust, visit Temperate Climate Permaculture.