I went to www.billnye.com which referred me to Disney. Here's their price list. I think these things are about $40/dvd. I think we'll stick with the library. (For some reason, the link doesn't highlight, but you can cut and paste or follow from billnye.com)

http://dep.disney.go.com/educational/search?form.keywords=Bill+Nye

Descartes Cove, however, sounds great. I wonder why CTY would undersell their own kids. Doesn't really make sense, unless they're coming out with something new.

http://cty.jhu.edu/cde/cove/index.html

Strange...