I have to plan my training because I'm working on the three disciplines of triathlon, so I need to work in (for now) 2 swims, 2 fast walks, 2 bikes and 2 strength training sessions. I just use a simple calendar template I downloaded from Excel, then log my training into Trainingpeaks (the free service). Of course, it's easier for me because none of my workouts are over an hour yet and I don't worry so much about speed.

But now it seems that my new personal trainer is going to work with me on that part of it.

I have no idea how much online planning costs, but you might want to see with a local coach to see how much different the price is.