i'm running a curve 8330 on telus, with an unlimited data plan, and a laptop with Vista. do I need anything other than the USB cable to use my phone as a modem?
If you have an unlimited data plan, which most of the major carriers already give you, then you can use it and you won't be getting any extra bills. I did it with my Curve 8320 (on T-Mobile), I just have the regular Unlim BB Plan for $20/mo.
You need a USB cable to connect your BB to your comp obviously, there is also a way to do it with Bluetooth but that requires your computer to also have Bluetooth, but that can get a bit complicated, slower than with the USB cable, and also will really drain your battery life fast.
Then you need to download the BlackBerry Desktop Manager program.
Check that link, follow the instructions, and it should work fine. Speeds are kinda slow though, I'm on T-Mobile's EDGE and I was getting like dial-up speeds, but maybe I just had a low signal, but could be faster on 3G.