This is going to be a really quick QuickTip today - if you've ever added a generic text field to a CCK content type to contain a phone number - stop it.
The super-simple Phone module provides a bunch of country-specific phone number field types. It automatically formats the numbers for display (you choose the separate and/or the area code delimiter) as well as validates the number (for several different countries). It even has iPhone support: if the page containing the phone number is being displayed by an iPhone, the module will automatically turn it into a link that can be tapped to dial the number on an iPhone. Sweet.
Comments
What about an international user-base?
I'm thinking surely you don't want to add every country available as separate fields. That will be one big form...
Is there not a way of having one field that says, if it meets at least one of these validators, then it a phone number? Or at least a type that can accept a phone number but at least checks that it contains only numbers?