I just made available a download containing a signed assembly (i.e. DLL for the non-.NET savvy) for the EXSLT.NET project. You can download it from here. Here's the elevator speech description of the project.

The EXSLT.NET library is an implementation of EXSLT extensions to XSLT for the .NET platform. EXSLT.NET implements the following EXSLT modules: Dates and Times, Common, Math,Regular Expressions, Sets and Strings. In addition EXSLT.NET provides own set of useful extension functions. See full list of supported extension functions and elements in "Extension Functions and Elements" section.

The project is primarily a merger of the code from my article EXSLT: Enhancing the Power of XSLT and Oleg Tkachenko's article Producing Multiple Outputs from an XSL Transformation with a number of enhancements from folks like Dimitre Novatchev and Paul Reid.

I'll probably write a followup article about this for my Extreme XML column on MSDN. In the meanwhile I assume Oleg will probably send out an announcement to xsl-list & xml-dev about the project in the next few days.