Power archiving with 7-Zip

7-Zip is a free file archiver with high compression ratio distributed under the GNU LGPL license. It's native format is the new 7z format based on the LZMA compression algorithm. Some of it's important features are listed below:

• Supported formats: 7z, ZIP, CAB, RAR, ARJ, GZIP, BZIP2, Z, TAR, CPIO, RPM and DEB
• 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 command-line version
• Options to perform incremental archive updates

7-Zip's high compression ratio make it ideal for backing up things on your disk. With the incremental archive feature, you can update only the changed files in the archive providing a quick way to perform frequent backups. You can get more information here, along with the downloads. There is also a Unix port (which works under Mac OS X and Linux) called p7zip. However this is only a command-line version. You may run the full 7-Zip GUI under Linux using Wine.