Alternative way to charge camera's Li-Ion battery?

The only way I know of to charge my camera's Li-Ion battery (the standard kind that looks a bit like an oversize domino) is to set it in the charging cradle and plug it into the wall. Is there an alternative way to charge this type of battery? Specifically, is there a way or mechanism that would allow me to charge this type of battery via my car's cigarette lighter or some type of solar source? Thanks.