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.
Speex is a patent-free compression format designed especially for speech. It is specialized for voice communications at low bit-rates in the 2-45 kbps range. Possible applications include Voice over IP (VoIP), Internet audio streaming, audio books, and archiving of speech data (e.g. voice mail).
The True Audio (TTA) codec is a simple realtime lossless audio compressor. It performs lossless compression on multichannel 8, 16, and 24 bit data of Wav audio files. The compression ratios depend on the type of music file being compressed, but the compression size will generally range between 30%-70% of the original. TTA supports both ID3v1 and ID3v2 information tags.
WebPack is a shell script for automatically packing Web sites by shrinking them without affecting their functionality or appearance. It is also useful for losslessly shrinking image collections and locating corrupt files. It works by stripping unnecessary information and optimizing the compression of images, and by removing comments/whitespace from HTML, using readily-available tools.
The FAAC project includes the AAC encoder FAAC and decoder FAAD2. It supports several MPEG-4 object types (LC, Main, LTP, HE AAC, PS) and file formats (ADTS AAC, raw AAC, MP4), multichannel and gapless en/decoding as well as MP4 metadata tags. The codecs are compatible with standard-compliant audio applications using one or more of these profiles.
Versatile Encoder allows you to encode your own videos into good quality DivX files. The input can be a sequence of files (as generated by blender), a single file (if you want to recompress something), or a VCD (if you need to back up a movie). This piece of software tries to guess good defaults and to help the user in making choices.