Links úteis
How .NET Regular Expressions Really Work Guia BEM avançado que mostra o funcionamento do motor das ERs no .NET
http://msdn.microsoft.com/en-us/library/20bw873z.aspx Matches any word character. Equivalent to the Unicode general categories [\p{Ll}\p{Lu}\p{Lt}\p{Lo}\p{Nd}\p{Pc}\p{Lm}]. If ECMAScript-compliant behavior is specified with the ECMAScript option, \w is equivalent to [a-zA-Z_0-9].
http://msdn.microsoft.com/en-us/library/system.text.regularexpressions.aspx System.Text.RegularExpressions Namespace
http://msdn.microsoft.com/en-us/library/30wbz966(VS.71).aspx
http://msdn.microsoft.com/en-us/library/kweb790z.aspx Exemplos da MS
http://oreilly.com/windows/archive/csharp-regular-expressions.html Tutorial muito bom do OReilly, com várias expressões prontas no final (cookbook)