This exploit was just recently (in the last hour) discovered, and Blizzard may be working to fix it, so don't flame me if they get it fixed before you get to try it, but I guarantee that it worked at one point in the last hour though.
The method:
Wear your desired gear and have any offspec/side grade items in a bag on your character. Have an empty bag in your bank and begin to drag the empty bag and replace the full geared bag on your character. Then take the empty bag from you char into your bag to swap for the geared one. Keep repeating this process always using the empty bag to replace the full one regardless.
Essentially you continue doing this and your stats just keep increasing. People have reported being into the millions in health and mana.
Take a look at WoW Forums -> [Exploit] Gear stacking. for more info,
G'night!