What exercises are possible when one has plantar faciitis?

I developed a pain in the bottom of foot (diagnosed as plantar faciitis by my doctor) quite some time ago, and I had to give up my favorite form of exercise, which is power walking. Since then, I’ve gained 35 or 40 ugly pounds.

I cannot afford a gym membership.

What exercises can I do that will not aggravate the plantar faciitis?

For the record, I don’t have time for swimming.