Once you've mastered the basics of kettlebell training there are a lot of different ways to increase the difficulty of your workouts.
Here is a link to an article I wrote on a couple of simple ways to change your kettlebell training to make it more effective for martial arts, military and sports conditioning.
Advanced Kettlebell Training #1
I'm a big fan of these types of training and I'm also a big fan of the gymboss timer which allows precise timing of these sorts of workouts.
We've just started stocking Gymboss timers so if you need one for your workouts jump across to our Training gear page and pick one up.