I've had some great success with bee balm attracting butterflies. What a showy perennial. It needs a good sunny spot to get established, but when it does.... I do try to plant this near a bird bath or water source as the butterflies will be more apt to rest in a place with both food and water.
I have some coreopsis planted in some containers that they really seem to love. Again, these are pretty near to a bird bath.
Gaura, specifically "Whirling Butterflies", attract both butterflies and hummingbirds. I have become a big fan of this perennial. Not only do they present these beautiful dainty flowers, but in the heat of the summer, they are usually crawling with hummingbirds.