A friend of mine who is a New ager and daughter of a Wikka preistess recently told me that the the reason they wear the ring on the left hand in the west is because there is a vain that goes from the left ring finger to the heart, making it a deep symbol of love.
This is actual a very ancient Roman (pagan) custom, I believe. I know in Italy the wedding ring is still worn on the left hand as a vestige of this ancient custom.
I'll be wearing mine on my left because my fiancee is Italian (Sicilian, to be precise) and her family is very much stuck in their traditions, some of which borders on superstition and bugs the heck out of me, but that's another thing. As Tom pointed out, it's the custom in this country, and one that has no bearing on faith at all.
At least it should not have a bearing on one's faith.