The Verizon iPhone data plan will cost $30 for unlimited data transfer. Unfortunately this will only be available for a limited time before Verizon moved to a tiered data plan structure though.

Additionally the 3g hotspot feature will be $20 a month. Like AT&T, tethering will not be unlimited, but it will pull from it's own 2gb worth of data transfer (regular data and tethered data pull from the same 2gb).