Audacity & Ardour—software

Audacity is a free, easy-to-use and multilingual audio editor and recorder for Windows, Mac OS X, GNU/Linux and other operating systems.
http://audacity.sourceforge.net/

FLOSS Manuals is a collection of manuals about free and open source software together with the tools used to create them and the community that uses those tools.
http://www.flossmanuals.net/audacity/

record
mix
edit
collaborate

http://ardour.org/

Gimp

GIMP is the GNU Image Manipulation Program. It is a freely distributed piece of software for such tasks as photo retouching, image composition and image authoring. It works on many operating systems, in many languages.

http://www.gimp.org/
http://gimp.lisanet.de/Website/Download.html

Hugin - Panorama photo stitcher

Goal: an easy to use cross-platform panoramic imaging toolchain based on Panorama Tools.
With Hugin you can assemble a mosaic of photographs into a complete immersive panorama, stitch any series of overlapping pictures and much more.

http://hugin.sourceforge.net/