BitJazz Inc.
Lossless compression for photoquality images. Cross-platform. SDK. Free reader.
http://www.bitjazz.com

WarpZip
Data compression utility for the OS/2 family of operating systems. Includes drag and drop implementation and speech enabled utility that deals with "zip" and OS/2 "packed" archive formats.
http://www.pillarsoft.net/

USENET Compression FAQ
This URL takes you to a compression FAQ that explains compression to technical people as well as describing the various programs, and what they do to users.
http://www.faqs.org/faqs/compression-faq/

SolutionSoft Systems, Inc.
E-Space, compression software for online archiving and disk space management.
http://www.solution-soft.com/

GZIPSite Website Compression
Tool that can help you make static HTML websites run 50% faster and save 50-80% of the bandwidth.
http://www.applet.dk/

QuikCAT Technologies
Specializing in data compression software technologies for wireless transmission, Internet acceleration, Microsoft Exchange and Lotus Notes E-mail acceleration, and PDA video conferencing, using cellular automata transforms.
http://www.quikcat.com

Archive Comparison Test
A set of benchmarks designed to show the state of the art in lossless data compression, by Jeff Gilchrist.
http://www.compression.ca/

1StepUnzip
Easy to use shareware tool for unzipping and installing your downloaded Internet files.
http://1stepunzip.com/

QccPack
Quantization, Compression, and Coding Library. C source code freely available.
http://qccpack.sourceforge.net/

ZipALot
Takes all the ZIP archives from one directory and extracts them to another one, allows you to handle more than one ZIP archive at once. Free open-source software for Win32.
http://www.ractive.ch/gpl/zipalot.html

FilZip 2000
Free application to handle a variety of archive file formats, including .ace, .arc. arj, .cab, .gz, .lha, .jar, .rar, .tar and of course .zip. (Win 9x/NT/2000/Me)
http://www.filzip.com/

Smacker Video Technology
A compressor for video, animation and sound data includes video compression with twice the video quality and now uses the Bink audio codec for perceptually lossless 8 to 1 compression.
http://www.radgametools.com/smkmain.htm

Automatic File Archiver by JSPayne
Does automatic archiving and backup of recently modified.
http://www.jspayne.com/filearchiver/

WinAce
Relative new though already used on many sites. When compared to WinZip the most important advantage of WinAce is better compression.
http://www.winace.com

RARReg
Offers downloads, support forums and registration for RAR compression tools.
http://www.rarreg.com/

JET-Software
Software house in Germany, with compression products for mainframe, midrange and mini systems.
http://www.jet-software.com/

Rarissimo
Companion tool for WinRAR for preserving NTFS alternate streams.
http://peccatte.karefil.com/Software/Rarissimo/RarissimoEN.htm

RICAZip
High performance lossless image compression applications, utilities and libraries.
http://www.ricazip.com/

ZipMail
Compression for Lotus Notes, that automatically compresses attached files into ZIP files or self-extracting files. Features full integration with the Lotus Notes email client software.
http://www.notes-compression.com/

ExpressZIP
ZIP and UNZIP Management complete with built-in Wizards to walk you through creating ZIP and EXE (self extracting) archives.
http://www.avantrix.com/exzip.htm

RAR/WinRAR support site
A support site for RAR and WinRAR archivers.
http://www.rarlab.com

ZBit Inc.
COM objects to Zip and Unzip files.
http://www.zbitinc.com

Video Compression Components
Third-party video compression software components for programmers.
http://www.imaging-components.com/

Zipsearch
Zipsearch is shareware to search compressed zip archives for files inside archives. The program finds text strings within the files for viewing and changes.
http://www.filehunter.com/ZipsearchDetails.htm

CoffeeCup Free Zip Wizard
Free Zip/Unzip utility. CoffeeCup Free Zip Wizard has built-in E-mail and FTP functions, so you can Zip and send your files in one easy step.
http://www.coffeecup.com/zip-wizard/

Maximum Compression
Aims to show the maximum achievable lossless data compression ratio for several filetypes (text, executable, bmp). The best 150+ programs for every filetype are shown in a table indicating compression ratio and switches/options used to achieve that compression.
http://www.maximumcompression.com/

7-Zip
Open source Windows utility for manipulating archives. Formats 7z, ZIP, GZIP, BZIP2 and TAR are supported fully, other formats can be unpacked.
http://www.7-zip.org/

x-PRESS
Delivers cross-platform data compression for data transfer, archiving, and retrieval.Part of the CoSORT family of sort and data manipulation solutions.
http://www.iri.com/public/solutions/xpress/xpress.htm

Hifn Inc.
Designs, develops, and markets compression processors, encryption/compression processors, and software which provide alternatives for the implementation of high performance networks and tape storage devices. (Nasdaq: HIFN).
http://www.hifn.com/

Zzip
A compression tool under GPL. Zzip compression algorithm is mainly based on the Burrows-Wheeler Transform method developed by Mike Burrows and David Wheeler.
http://debin.net/zzip/

ROG
German reseller of WinRAR, with information in English and German. Prices in Euros.
http://www.winrar-rog.com/

Xceed Software Inc.
Makers of Zip and Unzip data compression controls for Windows developers that use ActiveX, OCX, VBX and DLLs.
http://xceed.com

zlib
A massively spiffy yet delicately unobtrusive compression library.
http://www.zlib.net

CAM Development - CAM UnZip
Free zip file utility, which allows you to quickly, open, create, and modify ZIP archives. In addition, CAM Unzip supports password protection, and can run an archive's Setup file automatically after it is unzipped.
http://www.camunzip.com

PeaZip
Presents this free, open source archiver featuring volume spanning, authenticated encryption and compression in several formats. Includes download links, documentation and a support forum.
http://www.peazip.org/

Info-ZIP
Ffree, portable compression and extraction utilities for archives compressed in .zip format. Discussion forum, source code, and binaries for several platforms.
http://www.info-zip.org/