If you're using Ubuntu 9.10 a.k.a Karmic Koala now, although it's the Alpha version (The final will released October, 2009). You can easily to connect your cellphone to make it as the GSM modem with Bluetooth. Sure? OK, just try this step bellow.
First, make sure your cellphone support Bluetooth connection. Turn on your Bluetooth and active the show the device option (or make it discoverable). Then, connect your Bluetooth dongle to your computer, you will see the Bluetooth icon above. Click it, and select "Set up new devices..".
Second, press forward, then select your devices and click forward button again. Enter the code as seen in your computer screen to your cellphone for authenticate. Then give the mark on "Access the internet using my mobile phone".
Now you can open your browser and browse what do you want :D