I have plans (and a lot of seeds) for starting a new flower bed specifically with butterflies in mind... we have a good bit of milkweed that grows wild here; in fact, after checking the link to Everwilde that Melanie shared, I see quite a few of the types are native up here in the Michigan UP -- I was only aware of common milkweed and swamp milkweed. A few years ago I planted some of the common milkweed in my perennial flower bed that has mainly daffodils, coneflowers, daylilies, iris, and baptisia; might have been a bit of a mistake, but the butterflies were happy and for a couple of years I had LOTS of Monarchs and their cats; really fun to see literally hundreds of the Monarchs in my yard in the fall, grouping up and then gradually drifting up and over the trees and heading south... Unfortunately, though, for the past two years there have been hardly any of them around, I believe because the winters have been so extended. I'm hoping this year will be better again!
We have had a lot of the "Milkweed Tussock Moth" caterpillars -- which seem to come in large numbers and really strip the plants!