This is one that really surprised me. I happened upon it since I tow my 5th wheel with a diesel pickup and so end up at truckstops now and then. Inside many of them, you'll find advertisements and brochures telling you about their internet services. You'll also see a bunch of truck drivers sitting around pounding on keyboards. In general, I've found the drivers to be more than happy to discuss the "truckstop connection" with you and tell you the pros and cons of one service versus another. In general, you join one of these services for $10 or so per month, then can use their connections whenever you get to one of their truckstops. Some have PCs inside where you can sit and work, while most offer "in-cab" phone connections. One example is Park and View -- click the PNVnet picture to learn more about what they offer. TruckNet also seems like one worth checking out, with a truckstop directory and a discussion on their Truckstop Internet Kiosks. As I learn of more, I'll include them here. If you know of more, drop me an email line.
2003 Update: PNV site is still there, but TruckNet seems to now be just a site where truckers communicate and get a bunch of advertising.