Joe, I think the corrugated panels are nice but they can get real expensive. I'm trying to remember the name of the company that makes the ones at Home Depot. They are online, Tuf Something.
Anyways, Check out this Super Poly. Pretty amazing stuff
http://www.gardendome.com/greenhouse...poly_tarp.html
Or there are some places online to get the double walled poly panels for a decent price.
I think a wood frame with single wall on both the inside and outside with a nice air gap between is the best setup. If I had the room I would build a monster size greenhouse and have an indoor jungle!!
Mike