How Many Megapixels Are Needed to Print a Photo?

"I have a camera that's capable of more megapixels than I can fathom, and I know I don't need photos at such a high resolution, but I do want to be able to at least print full page photos. How can I determine how many megapixels are necessary to print a photo at a given size?"

Well, personally I never understood why people get confused, but I still cringe when I see articles that use PPI (pixels per inch) and DPI (dots per inch) interchangeably. Maybe it is the loose use of terminology that adds to the confusion? Check out the article, and sound off if you are still confused.