Two-dimensional graphics applications come in two main flavors: those that create and manipulate arrays of pixels (raster images) and those that work with more procedural elements that describe graphical information, points and curves (vector images). Because the latter of the two deals with a more abstract, mathematical representation, vector images are not subject to the quality variations and fuzziness that can come with raster images. This makes them ideal for logos, typography, and general graphic design.
In the world of vector graphics, the open source world has one primary answer for proprietary counterparts that work with this kind of data. That tool would be Inkscape.
Inkscape is an incredibly powerful vector graphics program that you can use to draw scaleable illustrations or edit vector artwork that other people have created. I've personally used it for creating everything from logos and business cards to posters and diagrams. With a bit of practice and the help of this cheat sheet, perhaps you can find uses for it in your own graphical toolbox.