[Gack! Blogger slipped a few cogs and relocated a post from sometime in summer 2012 to this date. No idea how to fix it.]
Meet the Orange Jewelweed (Impatiens capensis), a.k.a., Common Jewelweed, Spotted Jewelweed, Spotted Touch-me-not, or Orange Balsam. There's a yellow version of this plant -- Yellow Jewelweed (Impatiens pallida)-- that I did not realize is a different species. It commonly grows in bottomland soils, ditches, and along creeks.
According to the venerable Wikipedia, this member of the impatience family is North American native. If you're near water, you can see how the plant might have gotten its jewelweed name by immersing a leaf under water -- it appears shiny silver.
It gets its "Touch-me-not" name from the fact that its seed pods "explode" on contact.
Mug shots of the Orange Jewelweed, showing a face-on view and in profile: