I'm lucky enough to work where there is a large family restroom. EVERY time I visit (no excuses!), I set a timer to 2 minutes and do some intense cardio. This is enough to get my heart rate up and boost my metabolism throughout the day. Since I drink so much water, I burn about 150 calories/day!
This can be done at home too, as a way to sneak in extra cardio. Try jumping jacks, butt kicks, high knees, jump "rope", ab twists, etc. You can also use with strength training, such as wall sits, pushups, etc.