NChord is described as 'C# implementation of the Chord distributed hash table. The project provides a library containing the routing, lookup, and maintenance routines specified in the MIT Chord paper, and is quite stable including under heavy load and churn' and is an app in the File Sharing category. There are three alternatives to NChord for a variety of platforms, including Java, Linux, Mac, Windows and SourceForge. The best alternative is FreePastry, which is both free and Open Source. Other great apps like NChord are Open Chord (Free, Open Source) and Chordless (Free, Open Source).
Chordless is a Chord and DHash implementation written in java. It implements almost everything from Chord and DHash described at http://pdos.csail.mit.edu/chord/ , as well as some extra features such as transactions and remote method invocation.