Here is a new iOS 5 feature that hasn't been documented yet, most likely because it's probably a bug that will be taken care of in the next beta release. If you own a Verizon iPhone (aka CDMA version of the iPhone) and you go to Settings > General > Network > Internet Tethering, and turn the toggle ON, you will be able to tether your device for free, turning it into a Wi-Fi hotspot at no charge.
I don't have a Verizon iPhone so I couldn't verify this myself but I asked several people on Twitter and they were all able to turn tethering ON, without having to pay anything to Verizon...