You can also use Ham radio, if you have a ham license. Some SSB radios can also access Ham frequencies. SSB-based e-mail is not free, ham-radio-based e-mail is AFAIK
. SSB-based e-mail or Sailmail, is about $250/year.
Satellite internet is fairly expensive, since it is usually charged via data, not flat rate, unlike many of the cellular data plans which charge a flat monthly rate. Also, the equipment is fairly expensive, but has come down in price considerably in the last ten years. The monthly charges would depend much on how much you use the equipment. The equipment roughly ranges in price from $500–1200, depending on what kind of phone you want and what capabilities you want in it.
BTW, I'd avoid Globalstar as a provider, as I believe they're having technical and financial issues and may not be around all that much longer.
Cellular coverage along the US coast isn't too bad... but once you get out of range of the US-based cellular providers, the data plans are no longer flat rate IIRC, but charge per megabyte, much like the satellite data rate plans. US-based cellular provider rate plans are $45-60 per month or so. The equipment ranges in price. If you have a bluetooth equipped laptop and phone, then you have no additional equipment costs... if you want a PCMCIA card, then you're effectively paying for two cellular phone lines—one data, one voice.