For years and years and years I tried to balance cardio and weights, fitting in as many workouts as I could working 12 hour nights, and making sure I alternated the two to even it out. Now that I actually have time to workout seven days a week (by getting up at 4:30 AM on weekday mornings of course!), this is what I've been doing:
Monday - cardio (there's nothing quite like starting out Monday morning on the rebounder! LOL!!)
Tuesday - upper body
Wednesday - lower body
Thursday - cardio and weights (light!) in one workout (but mostly the cardio part since I just did two days of all strength training!)
Friday - core which often includes cardio portions, but the focus is core work
Saturday - total body strength training workout
Sunday - BOSU or fusion type workout, some of which include cardio portions, but the focus is balance work
I like doing something everyday, and I don't feel like I'm killing myself trying to fit it all in, nor do I feel like every workout has to be "killer" or intense since I'm doing something every single day. Also, if something comes up and I skip a day, I don't feel so guilty. I'm finding this works well for me, physically and mentally, and I'm going to try it for a few months and see what happens.
Carol