The Geospatial Data Abstraction Library (GDAL) is a unifying C/C++ API for accessing raster geospatial data, and currently includes formats like GeoTIFF, Erdas Imagine, Arc/Info Binary, CEOS, DTED, GXF, and SDTS. It is intended to provide efficient access, suitable for use in viewer applications, and also attempts to preserve coordinate systems and metadata. Python, C, and C++ interfaces are available.
Hodie prints the current date and time to stdout in Roman numerals, with grammatically correct Latin. Complete with Id., Kal., Non., pridie, postridie, bis, and all the other nice annoyances. As an option, it even provides you with current date according to Roman calendar -- that is 'ab urbe condita'; after Rome was built.
libgeotiff is a library (normally built on top of libtiff) for reading and writing coordinate system information from/to GeoTIFF files. It includes CSV files for expanding projected coordinate system codes into full projections definitions and examples of transforming the definitions into a form that can be used with the PROJ.4 projections library. It also includes the sample applications listgeo (for dumping GeoTIFF information in readable form) and geotifcp (for applying geotiff tags to an existing TIFF or GeoTIFF file).
PROJ.4 is a cartographic projections and datum shifting library written in C. It includes support for many (100+) projections, including Transverse Mercator and Lambert Conformal Conic. Included is a command line program for reprojecting points. It was originally written by Gerald Evenden of the USGS, and is in active use in various commercial and freeware software.