What do I use for graphic design?
For vectorial drawing i use Inkscape, an Open Source vector graphics editor, with capabilities similar to Illustrator, CorelDraw, or Xara X, using the W3C standard Scalable Vector Graphics (SVG) file format.
Inkscape supports many advanced SVG features (markers, clones, alpha blending, etc.) and great care is taken in designing a streamlined interface. It is very easy to edit nodes, perform complex path operations, trace bitmaps and much more.
If you want to learn using it you can start from the tutorials posted on the official weblog here: http://inkscapetutorials.wordpress.com/
You can get the software from http://www.inkscape.org/
For image manipulation i use The Gimp which is similar to Adobe Photoshop. The Gimp comes with alot of features such as Script-Fu, support for a wide range of file format, photo enhancement, animation package and many more.
You can download it from: http://www.gimp.org/
Both programs are available also for windows.
On the future I will post some nice tutorials here.