Rhino commons is a collection of useful .NET libraries and classes by Ayende Rahien.
Ayende describes it as follows: "Rhino Commons is a set of classes that I found to be useful in more than one project. It makes use of NHibernate, Castle, and various other tidbits that I have gathered in my travels. Rhino Commons is a library to help me do advanced stuff easier, and as such, it is advanced in itself."