I got them when I was training for a marathon and the only thing which helped me was stretching....a lot. Find a stair, put your toes of one foot on the edge of the stair and let your heel drop as low as you can stand it. Use you other foot to stand on the stair. After a minute or so, switch feet. You can also put all your toes on the edge of the stair and "stairmaster" the stretch very slowly with both feet at the same time while holding the banister. I did this every time I went upstairs.
I also agree with strengthening by going barefoot and especially walking on sand...it strengthens like nothing else.
GL! And hope it heels, ahem, heals soon!!