Walking has always been my exercise of choice. I don't need any motivation to walk; rather, I crave it. But I realize, too, that it's important to include strength, balance, and stretch movements into daily life.
In order to keep it interesting, I alternate among various exercise DVDs and videos, for about 20 minutes of supplementary workout several days a week.
Here's a series of smooth-flowing exercise and stretch routines from Ken Raupach, who trains triathletes in Australia. This one's for seniors, so it's gently demanding but not damaging!