Shade, sun, or both?
For full sun:
Rudbeckia and the traditional purple Echinacea are solid perennials that require little care and bloom first year. Even if the Rudbeckia's don't over winter they generally self sow easily. Several types of Coreopsis also are hardy or self sow. The fancier ones sometimes require some babying over the winter.
I have trouble getting most butterfly bushes to over winter for some reason.
Veronica's and salvias are also good choices.
Bluestone Perennials has a great "Plant Finder" feature that can be helpful for someone starting out. It asks you to fill in different parameters and will then generate a list of good options.
