7zip For Mac

7-Zip is designed for creating or unpacking archived and compressed files. The application can unpack 7zip, ZIP, CAB, RAR, ARJ, GZIP, BZIP2, TAR, CPIO, RPM and DEB files, or create file archives in those formats.
For the standard ZIP and GZIP formats, 7the application promises to deliver a compression ratio that is 2 - 10 % better than that provided by PKZip or WinZip, and the native 7zip format can provide a 45% reduction in file size from the common zip format.
Key features:
- High compression ratio in new 7z format with LZMA compression
- 7-Zip is free software distributed under the GNU LGPL
- Supported formats: Packing / unpacking: 7z, ZIP, GZIP, BZIP2 and TAR; Unpacking only: RAR, CAB, ARJ, LZH, CHM, Z, 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 File Manager
- Powerful command line version
- Plugin for FAR Manager
- Localizations for 59 languages

I use 7-Zip for Windows, and I am astounded at the quality of the compression (sometimes down to 55% of the original size). Is there such an alternative for Mac?
At the moment, I have a few DMGs, which would fit onto a DVD-9 but not a DVD-5. I can't get any good DVD-9s without ordering them online, and I don't want to go through that hassle for a spindle of 10 or 20. In addition, 7-zip would be an excellent format for archiving old data. Is there a mac version?