7-zip (7 Zip, 7-Zip Archiver, 7zip)

Website/Download: http://www.7-zip.org/
License: Freeware
OS: Windows
Latest Version: 5.0
Publisher's description:
7-Zip is a file archiver with a high compression ratio. 7-Zip is open source software. Most of the source code is under the GNU LGPL license. The unRAR code is under a mixed license: GNU LGPL + unRAR restrictions.