QCad is a powerful but easy to use 2D CAD program for Linux, Windows, and Mac OS X. It uses DXF as its standard file format. While other CAD packages are often rather complicated to use, QCad tries to stay comfortable, and even an absolute beginner can create professional drawings with a minimum of effort.
Tux Paint is a simple and entertaining drawing program geared towards young children. It has a simple interface, sound effects, and a cartoon character (Tux, the Linux penguin). Along with drawing brush strokes, lines and shapes, you can also enter text and place "rubber stamp" (or "sticker") images on the picture. Tux Paint is extensible, and could be useful in an educational environment (such as a grammar, elementary, or grade school). It's portable across numerous platforms, and runs well even on slower systems like the Pentium 133MHz.
Jaxe is a Java XML editor with a graphical document-oriented interface. It is configurable with an XML schema and a configuration file. It supports validation at element insertion, and is customisable with Java modules. XSL transforms can be used to export documents in XML, HTML, or PDF. Sample configurations include XML schemas, XHTML strict, Docbook, and DITA.
MuseScore lets you notate and compose music easily with your keyboard, your mouse, or a MIDI keyboard. You can print beautifully engraved sheet music or export it as PDF or PNG. You can play your score, transpose it, and save it as audio or MIDI file. MuseScore also supports MusicXML to let you share your composition with other scorewriters. MuseScore is often advertised as a cost effective alternative for Sibelius and Finale.
mtPaint is a simple GTK+1/2 painting program designed for creating icons and pixel-based artwork. It can edit indexed palette or 24 bit RGB images and offers basic painting and palette manipulation tools. Its main file format is PNG, although it can also handle JPEG, GIF, TIFF, BMP, TGA, XPM, and XBM files.
Jaikoz is a powerful tag editor that allows you to organize, edit, and correct thousands of audio tags with ease. Jaikoz has powerful automation features. Jaikoz uses MusicBrainz and MusicIP, online databases of over 5 million songs, which can match your songs automtically based on the actual music as well as the metadata. Jaikoz uses a convenient spreadsheet view to allow you to edit information very quickly and provides many autoformatting tasks which do most of the work for you.
gvSIG is an easy to use Java desktop GIS. It has a friendly interface, and can access some popular formats (e.g. SHP, DGN, DXF, DWG, TIFF, JPEG, ECW, SID, etc). It will integrate in a single view both local vector and raster data, as well as remote data through WMS or WCS. It allows layout design for printing. It is meant for end-users of geographical information, and currently has Spanish, Valencian, English, and 6 more interfaces. It's designed to be easily extended.
Kid3 tagger can edit the ID3v1 tags and all ID3v2 frames in MP3 files and the tags in Ogg/Vorbis and FLAC files in an efficient way. It is easy to convert between ID3v1 and ID3v2, set the tags of multiple files to the same values and generate the tags from the file name or vice versa. Import is possible from freedb.org, MusicBrainz, and other sources of track data.