An award-winning drawing program for children ages 3 to 12
Tux Paint is a free, award-winning drawing program for children ages 3 to 12. It combines an easy-to-use interface, fun sound effects, and an encouraging cartoon mascot who guides children as they use the program. Kids are presented with a blank canvas and a variety of drawing tools to help them be creative. Along with paintbrush, shapes and text, Tux Paint includes a "stamp" feature to add pre-drawn or photographic imagery to pictures, and a set of "magic tools" that provide filter effects (like blur, tint and waves) and interesting drawing tools (like train tracks, bubbles and grass). Tux Paint includes a collection of "starter" images, both coloring-book style and photo-realistic, and a large collections of stamps are available as a separate download. Additional content can be added by parents and teachers, or downloaded from 3rd parties. Tux Paint is available for Linux, BSD, Windows, Mac OS X and Haiku operating systems.
Audio converter and CD ripper for various formats
fre:ac is a free audio converter and CD ripper for various formats and encoders. It features MP3, MP4/M4A, WMA, Ogg Vorbis, FLAC, AAC, and Bonk format support, integrates freedb/CDDB, CDText and ID3v2 tagging and is available in several languages.
gPhoto is a program and library framework that lets users download pictures from their digital cameras. The libgphoto2 library gives you access to hundreds of models of digital cameras on several platforms. GIT repo and Issue tracker lives at https://github.com/gphoto/ these days.
Additional error correction for CD, DVD and BD media.
Sweep is an audio editor and live playback tool. It supports PCM (WAV, AIFF etc.), Ogg Vorbis, Speex and MP3, with multichannel editing and LADSPA effects. Inside lives a pesky little virtual stylus called Scrubby who enjoys mixing around in your file
ChemVisio is software which might be useful for educational purposes (non-organic chemistry, crystallography etc.). It might be a good visualization support for all people who need better illustrations than that you could see in books.
PPR is a spooler for PostScript printers. It supports PPD files, and provides operator alerts, job result messages, and error recovery. It is integrated with Netatalk, CAP60, Samba, and Ghostscript. It has command line and web interfaces.
computational renormalization group
YoSpin is a computational renormalization group.