Upgrading from:

NumericalMath`SplineFit`

All the functionality of NumericalMath`SplineFit` is now available in the newly created Splines Package.

To access functionality from the new Splines Package, load Splines`:

Version 5.2 << NumericalMath`SplineFit`;
pts = {{0, 0}, {1, 2}, {-1, 3}, {0, 1}, {3, 0}};
spline = SplineFit[pts, Cubic]