There are lots of options. Which one you choose will depend heavily on your cruising area and your pocketbook.
SSB weather broadcasts are done by the Coast Guard, WLO, and a number of other stations, including ham nets (like the WaterWay Net and the Maritime Mobile Net). A good list of net frequencies can be found at
Net / SSB Frequencies Weatherfax broadcasts are made from a number of stations worldwide, and can be copied with an HF receiver and the necessary software.
If you have
HF email (via a Pactor modem), you can download a number of weather products from SailMail (commercial) or WinLink (amateur).
Continuous weather broadcasts are done by NOAA stations all over the US and can be copied on your ship's VHF radio. These can also be copied at sea up to about 20 miles out, and are broadcast in many foreign countries.
There are hundreds of useful
weather products on the Internet. These can be accessed, if you're in range, via wifi or air cards. For longer distances you'll need a satellite-based system. Satphones (Iridium and Globalstar) can provide the connectivity needed to obtain Internet weather products.
These are only a few of the sources for WX while cruising. There are specialized products available also which can be useful, depending on your plans and preferences.
Bill