7-Zip is a file archiver with high compression ratio.

Usually 7-Zip compresses to 7z format 30-70% better than to zip format. And 7-Zip compresses to zip format 2-10% better than other zip compatible programs.

7-Zip Features
High compression ratio in new 7z format with LZMA compression
7-Zip is free software distributed under the GNU LGPL
Supported formats: 7z, ZIP, CAB, RAR, ARJ, GZIP, BZIP2, Z, TAR, CPIO, RPM, DEB and NSIS
For ZIP and GZIP formats 7-Zip provides compression ratio that is 2-10 % better than ratio provided by PKZip and WinZip
Self-extracting capability for 7z format
Integration with Windows Shell
Powerful File Manager
Powerful command line version
Plugin for FAR Manager
Localizations for 69 languages