Recently I started using T-Mobile's unlimited internet plan. It works nicely using the Motorola V600/Bluetooth with my Apple Powerbook. I find it quite addicting to be able to check the news, weather, send e-mail, and administrate servers from anywhere I have phone service.
The first beta of version 3.0 of the Horde Application Framework has been released. I highly recommend the horde suite to anyone who needs a web-based mail / calendar / addressbook solution. Go give the beta a try and report any bugs you find with it so I don't have to.