Here is my regiment if anyone is interested,
+Off trail running
+Mountain biking, I mostly stand the entire time, sitting only to get a drink, try it.
+Roller blade a couple of times to get some turns in and get your skating legs in shape for any skating you may have to do on your ski's (don't blow this off, you can blow your legs out skating across the resort just trying to get to another lift).
+Weight training, I only go once maybe twice a week and work
*Squats (or a machine that is similar.
*Spend time on those funny looking machines and open and close your legs, work both ways
*hold two weights in your hands and get into a tuck position for a solid 45 seconds, do 3 sets.
*Work your core, abs, (hit every machine and do some leg lifts, until you find out what you like), Lower back, and Sides
*arms, tri extensions are great and will help you with your skating, Dips are great also.
Find a cable machine that you can simulate a poll plant and push (skate).
And finally, anything else that you find helpful.
I usually spend 2 hours in the gym once a week and really focus on the running and biking the other days (2 days on one off, or 3 days on one off)) and blade once a week.
If you are planning a 4 day trip you will want to do a couple of weeks where you are running and biking 4 days in a row, just to get endurance.
The week prior to going I keep up the the running and biking until about 3 days prior to skiing. It's also important to start your workouts at least a month prior to going if you want to make the best of it, But anything is better than nothing and I am sure there are better programs out there, but this works for me (I also ski super hard and don't stop for lunch or anything when I am out). But Some times I don't do any training and pay for it.....
Several years ago I went BC hiking and skiing and wasn't in the best shape and blew my ACL out, it was 100% due to exhaustion, live and learn I say..