pngcrush is an excellent batch-mode compression utility for PNG images. Depending on the application that created the original PNGs, it can improve the file size anywhere from a few percent to 40% or more (completely losslessly). The utility also allows specified PNG chunks (e.g. text comments) to be inserted or deleted, and it can fix incorrect gamma info written by Photoshop 5.0 as well as the erroneous iCCP chunk written by Photoshop 5.5.
OzVM (Virtual Machine Project) is a simple, lightweight, secure virtual machine. The current target application of OzVM is OzStream, which allows platform independent self-decoding of data. The vision of OzStream is to make any and all compressed media self-extracting. OzStream abstracts compressed media from client applications, providing new freedom for users, developers, and compression techniques.
The lzlib compression library provides in-memory LZMA compression and decompression functions, including integrity checking of the decompressed data. The compressed data format used by the library is the lzip format. The lzip file format is designed for long-term data archiving. It is clean, provides very safe 4-factor integrity checking, and is backed by the recovery capabilities of lziprecover.
Lbzip2 is a parallel, SMP-based, bzip2-compatible compression utility, with a commandline resembling that of the original bzip2. It is usable both on its own and as a filter passed to GNU tar with the "--use-compress-program" option. It uses Gnulib, and its building and testing process is managed by the GNU build system. Starting with release 2.0, lbzip2 is independent of libbz2 and features yambi, an independent BWT compression stack with improved speed and robustness.
S3QL is a file system that stores all its data online. It supports Amazon S3, Google Storage, and OpenStack and effectively provides you with a hard disk of dynamic, infinite capacity that can be accessed from any computer with Internet access. S3QL provides a standard, full featured Unix file system that is conceptually indistinguishable from any local file system. Additional features include compression, encryption, data de-duplication, immutable trees, and snapshotting, which make it especially suitable for online backup and archiving. The design favors simplicity and elegance over performance and feature-creep. Care has been taken to make the source code as readable and serviceable as possible. Solid error detection, error handling, and extensive automated test cases are provided.
Shoelacer attempts to generate a pair of small C functions that compress or decompress a set of data (primarily short strings) presented to it, and possibly other data of that kind. The data it is given may consist of entries of just a few bytes or longer. Its goal is to be reasonably fast with a tiny memory overhead. Compression performance is not so much the goal, although it certainly isn't ignored.
xz is a data compression program using the LZMA algorithm and a similar user interface to gzip. Typically it compresses both tighter and faster than bzip2, and decompresses nearly as fast as gzip. The .xz file format includes headers and checksums, and also includes data filters (LZMA2) that can increase compression further.