I've blogged about Crossfit before. I have yet to join a box (mostly for financial reasons), however I do incorporate two or three Crossfit workouts a week into my schedule. Aside from the shear invigorating pain that a WOD can give you, I am a big fan of the foundational thinking and concepts behind Crossfit training.
I love the "World-Class Fitness in 100 Words" of the Crossfit mentality:
World-Class Fitness in 100 Words:
Eat meat and vegetables, nuts and seeds, some fruit, little starch and no sugar. Keep intake to levels that will support exercise but not body fat.
Practice and train major lifts: Deadlift, clean, squat, presses, C&J, and snatch. Similarly, master the basics of gymnastics: pull-ups, dips, rope climb, push-ups, sit-ups, presses to handstand, pirouettes, ﬂips, splits, and holds. Bike, run, swim, row, etc, hard and fast.
Five or six days per week mix these elements in as many combinations and patterns as creativity will allow. Routine is the enemy. Keep workouts short and intense.
Regularly learn and play new sports.
One of the things that I love about Crossfit is that it is structured to allow me to constantly challenge myself. The scoring, timing and scheduling always provides an opportunity for me to measurably improve performance.
Anyways, I could spend a lot of time trying to explain the methodology, however I'll leave it to Crossfit pioneer Greg Glassman in his article, "What is Fitness?"