An excellent article at eTrucker.com updates us on the status of Wi-Fi at rest areas: Texas has signed a contract to install Wi-Fi at 105 locations by Oct. 2005, with service free for the first two hours. They're hoping this encourages truckers and others to pull over a little more to catch up and reduce accidents, among other elements.
Michigan will roll out Wi-Fi at state parks, welcome centers, and rest areas charging $7.95 for 24 hours and $19.95 for unlimited access. (The article cites $7.95 for 24 sessions, which is taken from a typo in The State of Michigan's press release.)
Iowa and Wisconsin are also trying free Wi-Fi as part of a trial.