I was looking out for Regular Expressions for validating Phone Numbers of different countries. Here are some of them:

French Phone Number – (0( \d\d ))?\d\d \d\d(\d \d \d\d )\d\d

German Phone Number – ((\(0\d\d\) (\(0\d{3}\) )?\d )?\d\d \d\d \d\d\(0\d{4}\) \d \d\d-\d\d?)

Japanese Phone Number – (0\d{1,4}-\(0\d{1,4}\) ?)?\d{1,4}-\d{4}

P.R.C Phone Number – (\(\d{3}\)\d{3}-)?\d{8}

U.S Phone Number – ((\(\d{3}\) ?)(\d{3}-))?\d{3}-\d{4}

P.S: I did not create these regular expressions. If you are using ASP.NET and Visual Studio 2008/2010, you can easily get these expressions by dropping a RegularExpression Validator and browsing through the Regular Expression Editor ( Select the Validator > Properties > ValidationExpression)

If you are looking out for some more Regular Expressions, check out these two sites with plenty of resources on it Regular-Expression.info and RegularExpressionLibrary