The best by far is StormNow.com - Weather information via email, fax, pager and PCS.
I've used them since 1998 when they started. Absolutely dependable, highly configurable and inexpensive. The $2/month flat rate email option is perfect. There's also a two week free trial.
Many amateur radio operators, civil defense, homeland security, and city/county emergency coordinators use this service.
I live in a tornado/severe thunderstorm/hurricane prone area and would not be without this service
And NEVER any spam!!!