I am a runner, and have found relief with over the counter inserts and Thorlos running socks. An orthopaedic doctor indicated that the socks act as a sort of orthotic and the thick pads in the heel elevate the foot slightly and take some of the stress off of the plantar fascia. All of my fellow PF sufferers have my sympathy. Hang in there, and go with try anything that works for you. I would agree with those who caution against cortisone injections - use them ONLY as a last resort. Same with surgery. Most cases will improve with a combination of stretching, night splints, rest, anti-inflammatories and orthotics and/or inserts.
Happy Holidays to all.