@YoYo - Freedom of the Hills is an amazing resource. If you are specifically looking to train for higher elevation climbs, check out "Training for the New Alpinism". In addition, TrainingPeaks.com has some great programs. I used TrainingPeaks to train for a Mt. Rainier summit this past summer and it worked very well.
In short - lots and lots of stair climbing combined with aerobic and strength work.
Good luck and enjoy,