I found this in the comments section of this blog post: It is for those who cannot use eggs.
Egg Replacement - equals one egg
1/3 cup water
1 Tbls whole or ground flaxseed
Place the water and flaxseed together and allow to gel for about 5 minutes.
This mixture will bind patties, meat loaves, cookies and cakes as well as eggs do, but it will not leaven like eggs for souffles or sponge cakes.
Increase amounts accordingly for additional egg replacement.