I have to agree that cardio first impedes weight triaing intensity
I walk on a treadmill @ a speed of 3.8-4.0 for 10 minutes with a slight incline first, that gets the blood flowing and the heart rate up, then I do weight training, after that I do another 15 minutes of cardio. make sure you have a post workout shake within 15 minutes.
on cardio only days, I do 40 minutes split between eliptical stepper and treadmill. i occassionally throw the bike in there. I just moved and there is a high school right down the road with a big ass stadium, so i think i will be doing stadiums on saturdays.