How many oranges will one orange seed produce?

If you plan to grow an orange tree from seed, you'd better read this first:

http://ask.metafilter.com/62297/Help-me-germinate-my-citrus-seeds

You may get some kind of fruit after about ten years, but it will not resemble the orange that you got the seed from. How much fruit you get will depend upon how long the tree lives. A mature tree can yield several hundred oranges per year.