It's not a surprise that 12 years after Lisa Marie started this thread, the link she's provided has gone stale. However, her advice is still spot on:
Here's an updated link for the Stone Clinic's ACL Reconstruction Rehab Protocol. Their ACL Repair Rehab Protocol is different. While you are at their site I'd also recommend that you read this blog post about visualization skills helping speed recovery. Their info is light on ski specific drills, but this should really depend on your level of ability and is more in the realm of what a Physical Therapist should be working with you to develop. Your PT should develop a custom program for you. If your PT is not a skier, then either they should be consulting with a PT who is or you should be looking for a new PT. When it comes to developing ski specific drills for you, there are tons of threads in this subforum for general ski fitness that are examples of things a PT could focus on.
I am not a PT, but here is what I would be personally be looking for in general. First to consider is a mix of focus on improving aerobic capacity, strength, balance and flexibility. For aerobic development do activities that are fun for you. Personally, I golf at a hilly golf course (walking and carrying), play racquetball and rollerblade. For strength I would look for exercises that work adductors/abductors, quad and hamstring exercises that focus on optimizing the strength ratio (I use hammies 50% as strong as quads, but others recommend up to 75% as strong), hip, core and shoulder exercises (shoulder exercises also work the core and hips). I use free weights to do specific exercises given to me by a personal trainer so that I learned the correct methods. I use machines for general exercises that I've chosen for myself. I love Wall Sits (for 2 minutes), but check with your PT and consider doing a combo of a wall sit and a squat. Squats are great strength building exercises for skiers. For balance focus on single leg exercises with eyes open and closed and use fitness ball exercises. My favorite fitness ball drill is just sitting on the ball with your feet off the floor. A balance drill I use is the yoga warrior pose. For flexibility (beyond the knee flexibility the surgeon is watching) I would focus on ankle range of motion and hips. For ankle rom and balance, I personally use a balance board like the one shown here using single leg and both feet side by side drills to rock fore and aft and side by side with a pause in the middle (balanced position) with eyes open and closed. For hip ROM I use a medicine ball drill like the Russian twist shown on this list of medicine ball drills, but I hold the ball to the chest (make sure not to overturn the shoulders). I also do a drill laying on my back with one leg raised vertically and twist one foot from side to side to rotate my femur. An exercise series that I used during my own knee rehab (but is now replaced by playing racquetball) involves a series of cross over steps or hops forward, backward and side to side (e.g. box drill). When my gym had a slide board, I loved this thing and worked up to using hand weights while I slid. This is a cheaper version of using a machine like a Skier's Edge, Look for a mix of exercises on equipment you need to go to the gym to do and exercises you can do at home with a minimal investment in resistance bands, kettle bells, foam rollers, fitness balls, medicine balls, balance boards etc.
On snow considerations
Vermont Ski Safety has tips for knee friendly skiing. I highly recommend watching their ACL awareness video ($45). A lot of ACL injuries happen because of skiers caught "in the back seat". You can improve your fore/aft balance with drills like 1000 steps, 1000 shuffles (shuffling your feet instead of stepping), skating on flat ground, skate to shape (start skating downhill and slowly transition from skating to turning) and drills to keep your shoulders parallel to the snow surface. I love doing a stretch with skis on where you slide forward on one leg and touch one knee to the ground so that the top of the tip of one ski is touching the snow and the top of the tail of the ski is touching your shoulder (ouch!). Despite all of the work I did for my own knee rehab, moguls were the last step in the process. I felt great when I first got back in them but took it easy, quit after only a few runs and still was completely "knee exhausted" later on in the day.
Hope this is what you were looking for. It should give you lots of ideas you can pick and choose from.