This is from the Patient.co.uk site - where most NHS GPs print their info leaflets from here
Exercises
Regular, gentle stretching of your Achilles tendon and plantar fascia may help to ease your symptoms. This is because most people with plantar fasciitis have a slight tightness of their Achilles tendon. If this is the case, it tends to pull at the back of your heel and has a knock-on effect of keeping your plantar fascia tight. Also, when you are asleep overnight, your plantar fascia tends to tighten up (which is why it is usually most painful first thing in the morning). The aim of these exercises is to loosen up the tendons and fascia gently above and below your heel. Your doctor may refer you to a physiotherapist for exercise guidance.
The following exercises can be used to help treat plantar fasciitis:
Stand about 40 cm away from a wall and put both hands on the wall at shoulder height, feet slightly apart, with one foot in front of the other. Bend your front knee but keep your back knee straight and lean in towards the wall to stretch. You should feel your calf muscle tighten. Keep this position for several seconds, then relax. Do this about 10 times then switch to the other leg. Now repeat the same exercise for both legs but this time, bring your back foot forward slightly so that your back knee is also slightly bent. Lean against the wall as before, keep the position, relax and then repeat 10 times before switching to the other leg. Repeat this routine twice a day.
Stand on the bottom step of some stairs with your legs slightly apart and with your heels just off the end of the step. Hold the stair rails for support. Lower your heels, keeping your knees straight. Again you should feel the stretch in your calves. Keep the position for 20-60 seconds, then relax. Repeat six times. Try to do this exercise twice a day.
Sit on the floor with your legs out in front of you. Loop a towel around the ball of one of your feet. With your knee straight, pull your toes towards your nose. Hold the position for 30 seconds and repeat three times. Repeat the same exercise for the other foot. Try to do this once a day.
Sit on a chair with your knees bent at right angles and your feet and heels flat on the floor. Lift your foot upwards, keeping your heel on the floor. Hold the position for a few seconds and then relax. Repeat about 10 times. Try to do this exercise five to six times a day.
For this exercise you need an object such as a rolling pin or a drinks can. Whilst sitting in a chair, put the object under the arch of your foot. Roll the arch of your foot over the object in different directions. Perform this exercise for a few minutes for each foot at least twice a day.