Here's another excellent exercise for you: the Hindu Squat.
Wikipedia's take is pretty simple on the Hindu Squat.
“[The] Hindu squat - is done without weight where the heels are raised and body weight is placed on the toes; the knees track far past the toes.” --Squat (exercise) - Wikipedia

But look at the animation since it makes it so much easier to see an exercise being done verses reading the directions.

Most people won't be able to do many of these especially if you're not used to working out but the Hindu Squat is a powerful yet simple exercise for strengthening the lower body.