The USGS offers fifty software programs that are freely available. The programs can be browsed alphabetically or in five subject categories. Each program is accompanied by computer platform requirements, a summary of the program, readme files, pointers to decompression utilities, and documentation information (including selected downloadable user's manuals). Summaries contain pointers to other related programs, when available. Note that most software packages are available on AViiON DG/UX or UNIX platforms at present, but selected packages are available for other platforms as well.