I liked this as well:
http://www.organicgardening.com/learn-and-grow/apple-tree-pollination
If you have only one apple tree in your yard or incompatible varieties, all is not lost. Crabapple pollen fertilizes apple blossoms. So if you have a crabapple in the vicinity that blooms concurrently with your apple tree, you're in business. Grafting a branch of a compatible variety onto your existing tree is another option, though I recommend you hire an arborist to perform this job. You can also use an old, very effective orchardist trick, says Matthew Rogoyski, Ph.D., a horticulturist at Colorado State University. "Put a bouquet of crabapple branches in bloom in a 5-gallon bucket of water and place it inside the canopy of the tree," says Dr. Rogoyski. "Then bees can visit the crabapple blossoms and transfer the pollen to the apple blossoms."
I figure since my neighbors tree has apples there must be one somewhere close enough to theirs. Not sure what variety it is, but I may just buy a Crab apple in the spring, to plant. No one grows edible Crab Apples anymore.