In that case please note that for macports, a popular Mac package installer, the package names still contain the extra "s" and I guess should be made consistent at some point:
$ port search py27-scikit
py27-scikits-image @0.7.0 (python, science)
Image processing algorithms for SciPy.
py27-scikits-learn @0.12 (python, science)
Easy-to-use and general-purpose machine learning in Python
py27-scikits-module @0.1 (python)
provides the files common to all scikits
py27-scikits-statsmodels @0.4.3 (python, science)
Statistical computations and models for use with SciPy
py27-scikits-umfpack @1.0 (python, science)
Classes and functions for solving unsymmetric sparse linear systems
Found 5 ports.