Wikipedia was updated to remove all the implementation links, so for completeness sake they are here now:
- Detailed description of the Verhoeff algorithm
- A description using lookup tables
- Verhoeff implementation in Perl
- Verhoeff implementation in FileMaker Pro
- Verhoeff implementation in MS SQL Server Transact SQL
- Biographical sketch of Jacobus Verhoeff
- Verhoeff validation and generation code in C++
- Verhoeff validation & generation code in Javascript
- Algorithm Verhoeff validation & generation code in C#, VB.NET, VBA, Java, Python, D, PHP, ActionScript and Pascal/Delphi