Verizon's Wireless broadband is in 50 cities (or so they claim). Chances are, if you were in one of those locations you'd have access to either Cable or DSL. Go to their website and verify that it is even in your location. If it is, your best bet is to call them directly and ask if their card works in a Macintosh.
Verizon Wireless BroadbandAccess IS compatible with Mac OS X. The PC5220 has been compatible since 10.3.5 - 10.4.2. Apple built the drivers in, just stick in the card and it works, nothing to install. That card is no longer available. The card that DOES work is the Kyocera KPC650. I haven't found a PCMCIA Adapter that works with desktop Macs (I tried 3). But the cards work fine in PowerBooks with PCMCIA slots. The Kyocera KR1 Router will be the answer that you are looking for, we have a pre-production version and have tested and wrote a review at:
Verizon offers two services: 1.) NationalAccess (60 to 80Kb/s, 144Kb/s burst) and 2.) Broadband Access (400 to 700Kb/s, 2Mbps burst). The first option requires either a PC card or a compatible phone. The second option requires a card, only one of which is Mac compatible (management software). The model is the Kyocera KPC650 and it runs $149 (2yr) / $199 (1yr) depending on the length of contract you sign. You'll need to download the Mac version of the manager software, but you need your Verizon number before downloading.
Verizon's site used to (June 05) have info on the BradbandAccess with a Mac, but it's since disappeared. It does work on a Mac (Panther/Tiger are the only two I've seen it run on personally) as long as you're in the limited coverage areas. I know two people here in the Baton Rouge area that have it and use it on their PowerBooks.
I'm not sure about the NationalAccess working with a Mac, but it should. The card is compatible with both offerings and both use that manager software. That service is also available in more places than the other.
Here's a PCI to Cardbus adapter that is supposed to work with Macs (only ones with the genuine TI-1211 chips [which is what the PowerBooks used]).
Have you considered 2-way satellite? It's not cheap, but it's a viable alternative. Just make sure you look at 2-way systems (which most should be now-a-days). Older versions were download only, requiring you to use a modem for uploads. Some providers are: