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.
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.
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.
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.
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.
ArahPaint4 is a textile-oriented paint program, mainly for jacquard. It is a simple paint program for raster palette images. It has good tools for drawing images in repetition, support for handling palette images (color reduction, substitution, protected, transparent colors), contour tools, layer support, unlimited undo/redo, support for drawing in aspect ratio (pixels need not be square), a two level grid, and a coordinates display. It is simple, stable, fast, and works well on large images (>8000x8000).