Exercise Schedule Ideas?

Okay, I need some motivation. I've been going to physical therapy for a back injury, and I think my back is finally in a good state where I can start working out again. The problem is, I haven't been active in so long that I don't know where to start. Having done a couple half marathons in the past, I feel like doing anything short of running multiple consecutive miles is not a good enough workout and then I get frustrated and give up, yet, I am so out of shape and worried about my back that I need some more gentle activities than just pounding away for miles. Anyone out there have a "beginner-style" cardio and strength training schedule or program?? I think I need to just get on some type of schedule or have some type of goal in mind, otherwise, I have no push!