What kind of exercises are you doing? You can put a golf ball on the floor (or carpet for better stability) and roll the golf ball around using the bottom of your bare foot. Use under the arch, where the arch meets the heel, the heel and any areas that really hurt. Use as much pressure as you can stand and then a little more, It WILL hurt but you will get used to it. You can do this while watching TV or at work under the desk. I know MANY people this has worked well on! Also stand backward on a step with just your front 1/3 of foot on the step and the heel hanging over the edge. Slowly lower your heels below the height of the stair (Like your foot is sinking in the sand at the beach

) and hold it there and this stretches the achilles tendon and plantar fascia. Do a few repetitions.
When you are done, you can roll a frozen water bottle back and forth, from back to front. The ice will calm the foot down after the exercise.
Most importantly for plantar fasciitis....do not go barefoot. Use a heal lift or shoes with a slight heal, even cowboy boots--they work great!
I hope this helps.

Let us know if you feel any difference after a few times. I know it has helped some of my friends. Hoppy