butterfly garden advice

I am helping a friend plant a butterfly/hummingbird garden. I am very familar with hummingbird plants, as I have my own. I'm not as sure what to plant for the butterflies. Are there any must have plants? I am in zone 5b.

Here are a couple of links that I have saved. Maybe this will help. One of the lists has an old date, but it still has good info
http://www.sasionline.org/butgard/plants.html
http://www.uky.edu/Ag/Entomology/entfacts/misc/ef006.htm

PiggyPoo :0)

Here's a few good ideas from the UW - Green Bay:

http://www.uwgb.edu/biodiversity/biota/arthropods/insects/butterfly%20gardening.htm

Thanks! This helps a lot:)

I was trying to find something that spoke of putting salt down for the butterflies, and I ran across this. So I thought I'd shoot this over to you, as well as the others posted

http://hgic.clemson.edu/factsheets/HGIC1701.htm

PiggyPoo :0)

The Animal Planet did a show on Butterfly Gardening, and they did a puddling area (which could be easily modified). They dug a shallow hole, put in a plastic liner, filled it with sand (said ocean or salt-water sand would be fine - so I'm guessing sea salt would work with reg. sandbox sand), added water, and then a slurry of horse manure-compost (from local Home Depot, Lowes, etc) mixed with water, and added into the hole as well. The water was obviously not deep, and there were a few flat stones placed in the water for the butterflies to rest on while drinking. Flat pavers were put around the hole with pieces of watermelon flesh or other soft fruit for the butterflies to slurp from.

You could always use a shallow dish or trash-can top, buried in the ground instead of making a hole. And I would put the fruit in a dish with water to discourage ants, but the fruit wouldn't be something you would want to leave out overnight anyway....