Compression and Decompression

• 7-Zip
  http://www.7-zip.org/
• Comparison of File Archivers (Wikipedia) - note that "archiver" here means an application that packages together and compresses a set of files
  http://en.wikipedia.org/wiki/Comparison_of_file_archivers
• Filzip
  http://filzip.com/
• gzip (GNU Zip)
  http://www.gzip.org/
• Tar
  http://www.gnu.org/software/tar/
  http://www.openbsd.org/cgi-bin/man.cgi?query=tar
• WinZip
  http://www.winzip.com/