Packing and Unpacking with 7-Zip
Just for Windows: 7-Zip is an open source packing/unpacking application that goes with Window 98 to Vista. It can be used as a command line application, just as graphical user interface. Its major feature is the high compression ratio 7z format with LZMA compression.
It supports the following formats;
Packing/ Unpacking: 7z, ZIP, GZIP, BZIP2 and TAR;
Unpacking only: RAR, CAB, ISO, ARJ, LZH, CHM, MSI, WIM, Z, CPIO, RPM, DEB and NSIS. For ZIP and GZIP formats 7-Zip is said to provide a compression ratio that is 2-10 percent better than the ratio provided by WinZip.
You can also run 7-Zip off your thumb drive thanks to 7-Zip Portable by Portable Apps. So 7-Zip can be carried around and used on whatever Windows platform.
7-Zip is a free software, distributed under the GNU LGPL license