From the question Did any lightsaber ever run out of power? and DavRob60's answer to it, it appears that the diatium power cell in a lightsaber can be drained by a short circuit (and presumably through normal use) and then recharged again. How is the power cell recharged? Is it regenerative (turn the lightsaber off and it will recharge on its own) or does it require an external source of power like modern rechargeable batteries?
From the Extended Universe books, their power cell is like a modern rechargeable battery. Under normal Jedi use, they simply recharge their lightsaber once every few years. The lightsaber expends minimal energy when it's just on. It uses more when cutting through matter or deflecting blaster bolts. Since they're so efficient, and Star Wars power cells are so powerful, recharging isn't a frequent occurrence. And since it's pretty tedious to watch someone recharge their gadgets, it's pretty much never depicted in the books.
Although we don't see it happening, we can learn from the various Visual Dictionary factbooks that one of the ports on the side of the lightsaber is a "charging port" or "recharge plug". One assumes that it interfaces with common types of charging cables found in the Star Wars galaxy.
I submit that a light saber uses the same technology to harness The Force as midichlorines do. It's a receiver, basically, that channels and focuses The Force. It can be operated by a non-force enabled being, but becomes much more powerful when held by a Jedi, Sith, or envy other force-enabled person. As a side note, anyone with the technology can build a light saber, but a true Force User could pour a handful of sand in a bottle and make a light saber. IMHO