Adding another vote for hardy geraniums, especially 'Rozanne'. Blooms nonstop even when everything else has given up because of heat or drought or wet or whatnot!
One of my favorite vines has been the Coral Honeysuckle that I got in a trade... My Loncera americana honeysuckle blooms beautifully, once, and seems especially prone to aphids so its foliage gets a little scraggly. On the other hand, the coral honeysuckle on the other side of the deck steps blooms on and off (mostly "on" at least a few clusters) all summer long and even into late fall. It still has leaves now. And it makes a lot more berries for the birds, too, with all those blooms. And it does this all with very little attention from me, maybe a little accidental watering when I rescue-water something nearby.
