My son's college team works out at a place that makes use of CrossFit exercises to keep things fun and challenging. I've adopted many of these things into the more traditional weight-training/conditioning program with my HS team and they LOVE it. They actually look forward to the final 30-40 minutes of the workout day when they draw from the "Deck of Doom" (as I call it) which tells them what they are to do, and how many reps. I change it up for every workout.
They love the random draw aspect of pulling from a deck of cards. The Joker is the toughest pull. Our last Joker required whoever pulled the card to do suicides at every line they came upon down the full length of the gym the, once they reached the far end of the court, they did walking lunges all the way back. Now if a kid has already pulled the Joker once in a session, they don't have to do that routine again -- they can, however, give the card (and task) to another player of their choosing. I actually had three guys ASK for the Joker when guys who'd already pulled it pulled it again.
Anyway, you can find all sorts of great ideas here:
http://www.crossfit.com/cf-info/excercise.htmlIMO, the best part of CrossFit is that it integrates so much movement into what are otherwise just static exercises.