Free File Compression Tools
Free compression software for Windows distributed under the GNU LGPL, 7-Zip will pack / unpack 7z, ZIP, GZIP, BZIP2 and TAR; and it will unpack only RAR, CAB, ARJ, LZH, CHM, Z, CPIO, RPM and DEB.
TUGZip is a freeware archiving utility for Windows that provides support for a wide range of compressed, encoded and disc-image files.
IZARC supports a great many compressions formats. Rather than list them here I'll refer you to their webpage. The program also features Windows shell integration, encryption, conversion of different archive types and can be set to scan archives with an external virus scanner that you provide (i.e., the antivirus software that you probably already have installed).
This is a open-source program designed to create self-extracting archives for Windows from existing ZIP files.
Info-ZIP is a free package of Zip and UnZip compressor-archiver utilities available for a wide variety of platforms.
This is an open source file compressor. You can download the source tarball or the executables for a variety of platforms including windows.