I coded a program for inverse distance interpolation in Pascal (using Lazarus IDE) as part of the Programmming course at Czech University of Life Sciences.
The program is described in a 1 page long PDF manual and you can download it here: IDWinterpolator.
LICENSE: The IDW Interpolator (software) was created by Filip Kral. The software is provided free of charge and its usage is not restricted. Software is provided AS IS with absolutely NO WARRANTY OF ANYTHING. The author is not responsible for any damage arising out of use or inability to use the software. By downloading, using or storing the software you accept this license.