GDAL is a translator library for raster geospatial data formats that is released under an Open Source license. As a library, it presents a single abstract data model to the calling application for all supported formats.
Maintainer: Frank Warmerdam.
GDAL is in active use in a few projects, and includes a number of formats. Current translators include GeoTIFF (read/write), Erdas Imagine (read), ESRI .BIL (read/write), .aux labelled raw (read/write), SDTS DEM (read), CEOS (read) and Arc/Info Binary Grid (read).
I have created the gdal-dev@egroups.com mailing list. Subscriptions can be done, and archives reviewed on the web.
Incomplete (but useful) API Documentation exists for GDAL, and was created using Doxygen (as was this page).