Don't forget, for an added lower impact style, you can always put on your weighted vest (remembering to add the weight onto your body weight for your hrm, to get the true calorie burn
).
I like to do laps interspersed with jump rope (with or without a rope.) It makes me feel like I'm training for a fight.
I love bleachers too, I noticed those were mentioned. Outside is great for those walking lunges, no furniture to get in the way. I always like some high knees or some butt kicks for emphasis. I like to do intervals of a minute higher intensity/speed and then walk it or jog it down and do it again. I like variety.
I remember when I was a teen, I used to do a workout I found in a magazine.
200 m. run
(front lunges, side lunge, back lunge)
then do the other side/leg:
(front lunges, side lunge, back lunge)
Do it 20 times each leg.
Rinse and repeat until you are a sweaty mess.
These days, I am fond of Cathe's plie squats and also squat/kicks (side or front.) I also like to jog and do speed bag arms. I think thats the inner boxer coming out
If you are feeling adventurous and there is no one behind you, you might try jogging backwards a little bit for variety. I should warn you, this can produce doms. I do it on hills sometimes.