Audacity is free, open source software for recording and editing sounds. It is available for Mac OS X, Microsoft Windows, GNU/Linux, and other operating systems.
Blender is the open source software for 3D modeling, animation, rendering, post-production, interactive creation and playback. Available for all major operating systems under the GNU Public License.
The home of the GNU Compiler Collection (GCC). GCC is the primary compiler used on GNU/LINUX systems, and includes compilers for C, C++, Objective C, Java, Chill, and Fortran.
The home of the GNU Project. From this site, you can download a staggering array of sophisticated free (as in freedom) software applications. Among them is the GNU C library, which is part of every GNU/LINUX system
How to use GIMP like Photoshop, of course without all that hassle associated with Photoshop. Its easy and the learning curve is very shallow. You should be doing graphics quick and easy with GIMP, read this.