The bright orange butterfly weed (Asclepias tuberosa) is one of the most beautiful plants flowering in my garden. As I backed out of the driveway yesterday, I spotted an orange butterfly, perfectly mimicking the orange of the flowers, sipping nectar. It flew off when I got out of the pickup in an attempt to identify it (monarch and viceroy butterflies are the two most likely candidates). Later, I saw a spicebush swallowtail feeding on the butterfly weed.
Butterfly weed has another appealing attribute - it likes poor soil with no mulch, fertilizer, or need for supplemental water. I planted mine three years ago, never watered it after the first year, and it blooms beautifully.