Your poor little guy is probably teething or experiencing frustration at not being able to verbalize his needs. He is not biting to hurt you. And despite other moms thinking it's ok to bite back, I *strongly* disagree - please, please do NOT bite him back (and what does that teach him, anyway? that biting is ok?). You are more creative than that, and your son is more intelligent than that.
Instead, look behind the behavior and address the source.
If he's teething, help him use other things to bite on and relieve his pain (damp cold or warm washcloth, teethers, large carrot sticks, teething biscuits, etc.).
If he's frustrated and not able to express himself verbally, teach him some sign language - see http://www.signingtime.com (available at your local library? airs on your local PBS station?) or here's a wonderful, free online video dictionary of signs:
http://commtechlab.msu.edu/sites/aslweb/browser.htm
He may even need to pee/poop (often toddlers will get super antsy or irritable if they need to pee/poop but only recognize those physical sensations as discomfort), and at his age, you can certainly offer him the potty in a gentle, loving, non-coercive, no-pressure way. Sit with him, read him a book and let him relax/be distracted, run a little water from the faucet, or ask him if he can make a grunting noise. You'd be surprised that this works as often as it does. For more information on this:
http://white-boucke.com/reviews/latestarters.html
Best of luck to you!