Specter is an object-behaviour specification framework for .NET.
It enables behaviour-driven development by requiring developers to write executable specifications for their objects, before actually implementing them.
Technologically this is similar to test driven development, however the shift in nomenclature removes the psychological barrier of writing "tests" for code that does not exist. (Existing projects implementing this idea include RSpec for Ruby and NSpec for .NET)
Specter uses Boo meta-programming features and therefore allows very readable specifications to be written.