I am online at right now on a bluetooth connection from my PC through Sprint on my Treo 650. You need the latest updates, then DUN (dial up networking) shows up on the Treo's bluetooth menu. For me I bought an eBay bluetooth USB dongle for just over $10 shipped. I detected the treo from my laptop, set a 4 digit numeric pin and the devices were paired. Then I set up DUN with the id web, password web and told it to dial #777. I also shut off all the protocols on that connection except TCP/IP.
I am on it now and it is running over 2x dial up speed, about 120K actual (I configured the PC to talk to the modem at 230K). Quite respectable, no cords required, the phone can just sit in my pocket or on its charger.
Jim