Kirk - We have been using sailmail for a number of years and very happy with it
If your just going to do coastal cruising it maybe more cost effective to use a local cell phone carrier with a data plan. Like Verizon or AT&T. We used Verizon and using our cell phone was able to connect to the Internet and send/receive email. After 9pm and on the weekends it was free minutes
If your headed off shore then you will need to obtain:
1. Pactor III modem
2. Cables, ferrite chokes
3. 500W Line isolator
The above three items will run about $1100-$1200. Download airmail software program for free from sailmail.
If you're a ham then email will be free using winlink
If you are not a Ham then sailmail is $200 a year. But you will need a FCC assigned call sign. Not sure what the cost is. Also not sure if you're in Aus, SA or NZ they have the equivalent
If you want to get right into it then check out http://ssca.org/DiscBoard/
and go to there communication section. Lots of very technical advice available there.
Also you may want to review http://sailmail.com/
especially their primer download. Follow the installation to a T and you will not have any problems. Especially about using the chokes and line isolator. It is very easy to get stray RF running around when transmitting data and it can cause problems.
The great thing about airmail is you can get so many things in a semi automated way. Weather faxes sent to you, Tsunami warnings, grib files and even web pages like Latitude 38, etc. Plus there is a drop down panel for submitting location reports to Yotreps. The choices are numerous.
Thats the condensed version. My how things have changed in email communication over the years.