Everything what you have to do is:
- Configure bluetooth in phone
- enable the bluetooth
- turn on the "Internet sharing" application
- estabilish the connection
- Configure a Linux host
dhclient -1 -d bnep0
More info about the configuration for Ubuntu can you find here:
http://www.geekzone.co.nz/
http://ubuntuforums.org/
http://forum.eeeuser.com/
http://ubuntu-utah.