Spline, B-Spline and NURBS C++ library

Question

Does anyone know of a library or set of classes for splines - specifically b-splines and NURBS (optional).

A fast, efficient b-spline library would be so useful for

Answer 1

I know I'm answering months after this question was asked, but for others who might be searching for a similar answer, I'll point out openNURBS.

OpenNURBS also happens to be the library used in the modeling package Rhinoceros. It's a very complete library and it's worth consideration.