Are there any effective defogger solutions for scuba masks?

Masks will sometimes fog over while diving, making it difficult, if not impossible to see.  To defog the lens, three things work best.  For instance, you could purchase a commercial product from a local dive shop or online.  This type of defogger product is inexpensive and most brands work well.  Another option would be to carry a tube of gel toothpaste and apply a small amount followed by rinsing in freshwater.  However, a popular choice is simply to spit on the inside of the mask lens.  While it might sound crude, for some reason spit works amazingly well.