Alternatively you can look at buying a home version of the sorts of cardio machines you find at your local gym - a rowing machine or stepper for example. You don't have to spend a fortune on these, however.
Rather than diving straight in and buying the most expensive top of the line model, look around for bargains - there are always plenty of deals to be found in your local newspaper, at boot sales, or on e-bay.
Be sure to test any cardio machine before you buy it, to be sure it works properly and is the right size for you, and make sure to measure both the machine and the space you have available - these machines can be surprisingly big when you start trying to shoehorn them into your living room!
Finally, you could put on your favourite music and dance, or use a keep fit video of some kind (aerobics, yoga, Pilates etc). A quick look around Amazon or E-bay will offer a huge variety of home workout videos and DVDs. Whatever your tastes, you'll find something out there to suit your needs.
The great thing about doing your cardio workouts at home is that you can do them at a time to suit you. Indeed, many home exercisers do the majority of their workouts in front of the TV. It's amazing how much quicker a hard cardio session goes when you're watching a football match or an episode of Eastenders!
So don't let your budget or schedule stop you from getting in shape. Figure out which of these will work for you and get cranking. Time for CSI? Must be workout time!