Interval Tree
A C# implementation of an interval tree datatype based off the description in Introduction to Algorithms (Cormen, T. H., Leiserson, C. E., Rivest, R. L. & Stein, C).
How this implementation might differ from others is that is implemented as a generic type (specifically IIntervalTree<T>).
This allows you to get interval tree behavior on your already-existing business objects that may already represent intervals of some type.
API documentation can be found here.