I guess that you have already sorted this. I just wanted to add that many people have 3.5g enabled phones that they can use as a modem with out the need for taking out another contract.
Please check to see if this is allowed by your telco- I am with T-mob and have web and walk pro tariff on my phone which allows me to use it as a modem for about £8 pm (as well as allowing me to access the network on my phone). this is cheaper than a seperate dongle and contract.
I have a windows mobile phone so I can create a "hotspot" to enable more than one pc to share the connection or i can use bluetooth or usb.
The downside is that you can't make phone calls at the same time and battery life.
Iphone users are not allowed to do this (and many other things) under any circumstances. That said they can do it if they "jail break" their phones first.