Reddit mentions of The Illustrated Guide To Snowboarding

Doing squats (with weights) and wall-sits also helps, although your legs are probably strong enough from skiing. Honestly, since you're a competent skier you're probably better off spending less time in the gym and more time on the mountain.

This book helped me a lot my first year:
http://www.amazon.com/Illustrated-Guide-Snowboarding-Kevin-Ryan/dp/1570281440/ref=sr_1_1?ie=UTF8&qid=1291094123&sr=8-1

The language and illustrations are super-cheesy and your buddies are going to make fun of you when you're reading it in the lodge, but the fundamentals are described pretty well. It's also cheap: $12.

Keep yourself low (like you're pooping) and get used to having one edge at a time. You'll do great.