If you're planning your own butterfly garden, or looking to add to it, keep in mind that most of these plants do well in full sun (with the exception of impatiens). Now is a good time to add some of these perennial plants and annuals to your garden. I'm still working on this myself. Most of the plants pictured were planted recently, and some more are waiting in flats, ready to be planted today.
Also listed are trees and shrubs, although keep in mind these are probably best planted in the fall.
Lantana
Verbena

Not pictured: chives, daylily, hibiscus, sage
To add in the future: Milkweed, Bee-balm, Black-eyed susan, Butterfly weed, coneflower, phlox
Trees and Shrubs
Redbud

Buddleia ("the butterfly bush"; the #1 attraction in my yard)

To add in the future: Blueberry, Abelia
Annual plants
Impatiens

Zinnia and Verbena

Not pictured: Cosmos
Food plants for catepillars
Fennel (dill, carrots, and other plants in this family will work, too)

Not pictured: Dogwood, Parsley, Oaks, Tulip Tree, Snapdragon
To add in the future: Milkweed, Asters
For more information:
Clemson University Extension's on-line publications on Butterfly Gardening, Annuals, and Perennials.
Why flowers come in colors
So a butterfly flew into a bar...
Coming soon: Gardening to attract other animals, like bumblebees and hummingbirds