Have you ever wondered where the name "box elder" tree comes from? According to the Ohio State Extension, the common name "box elder" probably "refers to the use of the softwood in box making." Note that the Latin name for box elder trees is Acer negundo, whereas the true elder, whose fruits yield elderberry wine, is classified as Sambucus canadensis. Despite owning a similar-sounding common name, "alder" trees (genus Alnus) have nothing to do either with elderberry trees or box elder trees.
Box elder trees are really a type of maple. Steve Nix says that, like silver maples, box elder trees have weak wood, which may make them undesirable to some homeowners. If you'd like to learn more, read the full article on box elder trees from About.com's Forestry Guide.
A while ago I came across an amusing article on box elder trees written by Larry Ahlman. Called "Close Encounters: My Terrible Box Elder," Ahlman's humorous tale relates his experiences with a huge old box elder tree that span the decades of his life.