StateVis is a package that allows states (or groups) to create a browsable database of their Landsat holdings.
Zipdy is a program for calculating the distance between two zip codes and finding all the records in a RDBMS with a zip code with x miles of another zip code. Zipdy was written in C but is also available in PHP and perl.
Cartography tools for ARC/INFO
AML and C code and documentation for cartography within the ARC/INFO geographic information system.
given three point that are not co-linear in the object or image space return a rotation matrix and offset that allows image points to be projected back into object space.