I would think taking off at least a month before starting again is a good idea, it would help up the "shock" factor to your muscles when you start again.
Definitely search for the threads on the undulating rotation, it's a great way to even mix it up more. I had started one after my first 3.5 month rotation, and was really enjoying the variety, but had to stop after 4 weeks into it.
I believe Christosz has posted his undulating rotation in the workout manager available for download.
I too am finishing the 3 month rotation. After taking about a month off to do circuit workouts and gym style workouts, I will start an undulating rotation again(this will be the second time). I love the undulating rotation. It provides variety and I saw awesome reusults with this rotation.