After tearing my left knee ACL on Monday while skiing in Utah, I am pretty bummed about losing out on the upcoming climbing season. Any suggestions on how to train/climb despite the injury? (I will have surgery on the knee fairly soon). I have access to a climbing gym and even a woody and rockrings at home.

Well there is a positive to this. You have a fairly unique opportunity to practice movement/isolation of one specific body part. Pick routes that have ample foot holds and practice (maybe start with medium size hand holds and larger) climbing on the one foot. Ideal? No, but its physical training (helping maintain your climbing specific adaptations) plus you are "forced" to isolate one leg over the other, one hand/arm over the other, etc. Just like one arm traversing but with one leg. Also feet off bouldering and hangboard workouts are fine. There's probably many more options if you use your imagination.

Also traditional pull ups and frenchies! When you're lame leg gets better you're upperbody will be more than ready. I don't know even what type of climbing you prefer but use this time to read (rock warriors way, how to manuals, etc) and work on your racking system, anchors and rope management techniques (lap coils, coils in a sling, etc). Use this time wisely and you'll be back in no time stronger (minus the lowerbody perhaps) and more practiced in various techniques (rope management, anchor craft, etc).

After surgery just hangout and watch climbing DVDs - your knee is going to hurt. Once you have the option of partial weight bearing then do some easy stuff on your rock rings to maintain finger strength but make sure they are at a reasonable height so that you can get on/off of them in control. As far as bouldering in general I would wait until your cleared from the doctor - you could easily tweek it and be right back to where you started. Your knee is going to be quite sore for a few weeks just from surgery and even after that bumping your knee into anything hurts pretty bad. You should probably just start with top roping once you get the go ahead for full weight bearing. I've had 2 knee surgeries (not ACL or tendon related) and I didn't really do anything climbing related during the recovery process and the losses I had in strength and whatnot were recovered within a few months.

I tore my ACL and menisci and had surgery this past October. It was rough for me. Recovery for me has been long. I can't fight wildfires this summer, so I lost my job. Obviously, no skiing/riding till next winter which sucks. Surgeon won't let me climb for another 5 weeks or so. I also hate to be waited on by others and be disables. It took away a lot of confidence/pride I had. My knee is now at 80% now and I've been running a bit which is enjoyable now after so long not being able too.

Try to keep off the weight. I've haven't used my time like The Stoned Master recommends. It will come especially when you are on crutches and can't do much. The surgeon actually told me I couldn't do anything besides rehab for a few weeks/months. I ended up starting to brew and drink quite a bit. I've been lifting weights also.

Steph Davis had ACL surgery and was back at it a lot sooner than I am able too, so your mileage may vary.

After 2 knee surgeries and a ruptured achilles repair I feel your pain! I did a lot of pull ups on my finger board and I also have a bowflex. I alternated days and work outs. This was also a key time to do some mental training. It is really hard for me to sit still and after my achilles repair last year I thought I was going to go nuts my foot was immoblized for almost 7 months!
Try not to do anything that will put unecessary pressure on the knee, but you might be able to do some straight leg raises to at least keep some muscle around the quads. Otherwise Let it heal and do what they tell you to do. (Reason I had a 2nd knee surgeries is because I didn't give it the time needed to heal)

I don't know how useful your knee is/will be, but if I were in your position, I would probably set up a hangboard and put that to use for some strength gains, without putting the knee at any risk. I'de probably use the remaining time to try to do proper knee rehab until I was confident that weird positions/landings wouldn't re-injure, and maybe work on overall body weight management.
Pullups and watching climbing dvs/reading would be less beneficial for your time as far as training goes, but sounds great if you have extra time to kill.

These are all great suggestions, guys. Many thanks. I'll keep you posted!