Official exercise mats and jump mats can be pretty expensive. When I'm at home, I like to run in place, do jumping jacks, and jump rope while I watch TV. The impact from the floor can be damaging to the body, so I stack a bunch of my mats (many from the dollar shop, even) on some carpets to lessen the blow. It's also good to wear your sneakers, too.
Instead of purchasing a kettlebell, use a large empty plastic laundry bottle filled with water. Tighten the cap before each use to be sure it is on tight.
Looking for cheap or free exercise equipment? Visit garage sales. After a weekend or two of going to garage sales in your area you probably could outfit your own gym for as much as it cost to buy one treadmill at a sporting goods store.
Some folks think that you have to have a bunch of expensive exercise equipment to get a good workout. Walking is completely free, just start doing so.
Make your own weighted exercise balls by slitting opening 2 tennis balls and filling with pennies. Once full, cover the slit with duct tape! Voila! An exercise helper for "pennies" a day!
Foam rollers are all the rage now for after workout muscle pain relief, therapy, and injury prevention. I bought mine online for around $30 and cannot be without it.