Creating WFPC2 Darks describes how WFPC2 darks are made. Includes downloads for users to generate darks.
A paper on "An Improved Distortion Solution for HST's WFPC2" by Jay Anderson and Ivan King is available at the PASP website. There is also a text file containing a Fortran routine that implements the Geometric Distortion solution. A new (October 2009) geometric distortion file is available for retrieval on the CDBS WFPC2 IDC file web page.