For the C# Language
The following web sites hold published standards for the C# language. In some cases, for obvious reasons, these overlap extensively with general .NET coding standards.
The guidelines published here are used by Microsoft for their own samples and documentation.
In addition to coding guidelines, Aviva also publish their static analysis rules and recommended ReSharper settings.
TIOBE make the commercial coding standards from Philips Helathcare available. The format ofthis document is particularly interesting as it has a very formal rule numbering convention.