Yes, there are a ton of organizations that offer adaptive snowboarding programs! For a listing by state, check out DSUSA:
http://www.dsusa.org/chapter.html
This is not a complete list, so you may want to google if you don't find one in your area.
If you are in Colorado, I'll put in a plug for one of the best programs in the country: Adaptive Sports Center of Crested Butte (www.adaptivesports.org)