Spline, B-Spline and NURBS C++ library

This library may also be promising: http://libnurbs.sourceforge.net

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.

Eigen Spline is based on the famous (fast) C++ template library for linear algebra.

1.) For B Splines - You should check Numerical Recipes in C (there is book for that and it is also available online for reference)

2.) Also check: sourceforge.net/projects/einspline/ & this

-AD