For rooted devices I like this one:
code.google.com/p/android-wifi-tether/
It is very stable and works well with this phone. The only downside is it currently does not support infrustructure mode with our phones. Not an issue for connecting a computer, but if you are wanting to connect other phones, tablets or gaming systems you won't be able to because it only supports ad-hoc mode.
If you do tether a rooted device without paying for the feature it may be technically thieft of service, it will violate your terms of service, and it could result it Verizon canceling your service. Has anyone ever heard of this actually happening?