Butterfly Bush is probably the best all-around butterfly magnet you can find.  I grow the variety "Black Knight."  They grow about 7' tall if you cut the stems back to about 6"-10" in early spring.  Left unpruned, they may grow 14' tall and just as wide.  Pruning is said to cause the plant to be more floriferous.  Black Knight butterfly bush blooms from late June or early July through September.  The flowers give off a very pleasing aroma.  When removing dead flowers, it is better to cut back to just above some strong flower buds.  This will result in larger flower clusters.  Hummingbirds will take nectar from butterfly bushes.  You might also see the Clear-wing Hummingbird Moth doing the same thing.  It looks more like an elongated bee than a moth, and acts just like a hummingbird.