You can find their source code in codeplex at the ASP.NET source code.
ExtendedMembershipProvider: http://aspnetwebstack.codeplex.com/SourceControl/changeset/view/553690ac9488#src/WebMatrix.WebData/ExtendedMembershipProvider.cs
SimpleMembershipProvider; http://aspnetwebstack.codeplex.com/SourceControl/changeset/view/553690ac9488#src/WebMatrix.WebData/SimpleMembershipProvider.cs
购物小站点
http://nopcommerce.codeplex.com/