Swimming and biking are ace for stamina, and jogging is another.
With swimming, I recommend 1,2,3,4,5 or however else you'd like to do this (it's customizable). One length, then rest. then do two (there and back) and so on up to five, then go down. So start with 5, then do 4... you get the idea.
This is a good one for building up jogging/ general stamina: The 8-Week Beginner's Program | Runner's World
It gets you to run at your own pace, the aim is to be able to run 2 miles comfortably without stopping in 30 minutes. Seems a bit pathetic sounding to some ("only 2 miles?!") but it really does help! You could also apply this to your bike as you'd be able to keep the speed you would running on your bike.
I'm hoping I explained this okay, if I haven't and you'd like me to explain better or elaborate then let me know ^^