Compression/Archiving/Backup [compression]

Software 7-Zip
File Format ARC archive
Websites Archive Comparison Test (ACT)
File Format ARJ Archive
Books Compression Algorithms for Real Programmers
Books Data Compression - The Complete Reference, Fourth Edition
File Format GNU Zip
Software gzip (GNU zip)
Books Managing Gigabytes - Compressing and Indexing Documents and Images
Software PkZip 4.5 Suite
Blog Entry Podcast about the ZIP file format
Software StuffIt Deluxe 7.5 (Windows)
Books Text Compression
Books The Data Compression Book, 2nd Edition
SDKs Universal Compression Library (UCL)
File Format ZIP archive
SDKs zlib compression library
File Format ZOO compressed file