This web site does a decent job of explaining what the differen pain relief options during childbirth are. I thought others here might be interested in it. Some important things are missing from it that you should be aware of - first, it doesn't discuss the natural labor process well; since the site is written by an anesthetic organization, obviously non-anesthetic pain-relief/management techniques are not covered.
Last, they downplay the effect of anesthesia's on the baby (they obviously think of it in medical terms such as baby's apgar scores rather than ability to breastfeed, etc.), at least that is my opinion.
It does a good job of explaining what the different medications are and how they work, though.http://www.lcanesthesia.com/labor.html#epidural