I have lots of nice perennials that grow in shade but none that flower all summer. If you want something that flowers all summer in shade try impatiens. They turn to mush at the first frost but sometimes they'll reseed themselves next year. Or you can just buy more and plant them after the last frost around Mother's Day. Golden foliage will brighten shady areas. Hostas, Hakone grass, golden creeping jenny etc. If you don't know much about gardening you might ask someone to look at the area in question and see if there are any good plants in there buried in the weeds. Also you should go to the fall swap and get lots of advice and free plants. Go to the Exchanges page and get the details.

Our native Impatiens species, Impatiens capensis, called Jewelweed or Touch-me-not, has orange flowers with a long bloom time, June or July to September, and thrives in moist to damp shade, often spreading to cover large areas. Impatiens capensis is an easy to grow, re-seeding annual.

http://www.missouriplants.com/Redalt/Impatiens_capensis_page.html

http://www.ct-botanical-society.org/galleries/impatienscape.html

http://www.mobot.org/gardeninghelp/plantfinder/Plant.asp?code=K490

For dry, light shade (maybe the less shady areas of your garden) you might consider Heuchera cultivars for colorful foliage. Heuchera are low maintenance, clumping perennials, and the variety of foliage colors that plant propagators have developed in recent years is really amazing. See for example the selections on this page:

http://www.lazyssfarm.com/Plants/Perennials/H_files/H.htm

Shade gardening is a pretty big topic. What you can grow depends a lot on how dense the shade is and how much competition you have from tree roots. For a dappled shade environment without a lot of competition for water the list of plants is very long (many "sun" plants will do fine in this environment and most flowering evergreen shrubs like some shade), but the north side of a wall shaded by a large maple will challenge any gardener.

Since this area has been neglected and is overgrown, I would take that as a positive sign that plants can live there without a lot of supplemental watering. Before you start ripping things out, identify what you have. You may be able to save many of the plants or at least use them to determine what you should purchase (and keep an eye out for poison ivy).

- Brent