when i did a google search a few weeks back on the same topic (snowboarding exercises) i think the three sites i found all said:
1. lunges
2. squats
3. core work (crunches/situps, especially done on one of those inflated balls)

balance exercises... standing on a Swiss Ball, using an IndoBoard (specialized surfing/snowboarding/skateboarding balance trainer device www.indoboard.com/)

various yoga balancing poses like Tree

standing on one foot while watching TV.

the 'quieter' your body can be while on these unstable devices / in these unstable positions, the more stable you'll be when sliding ice, floating in snow, etc.


also practice FALLING. i.e your tumbles, somersaults. On soft grass. If you get in the habit of rolling/somersaulting when you fall, you'll avoid a lot of injuries (compared with stopping yourself dead with your arms, for example), and after your tumble, with luck, you're right back on your feet ready to continue on your way. It's a great feeling when this happens!

Add some sit ups or some type of ab workout as well-mine are usually sore after a day on the slopes from strapping in and out all day. Stretching is always a good thing too.

For exercise, I think it's all been said as far as I know.

But! Dieting / vitamins are also an important part of it.... The bones in your legs, calves, feet, etc. take a lot of loading. Remember to get calcium and protein to repair your muscles faster!