Inkscape is the master of vector graphics. It blows even expensive, proprietary applications (like Adobe Illustrator, granted, I haven’t use that in many years), out of the water.
If you don’t know what a vector graphic is, think about all the images you see that aren’t photos taken with a camera. Logos for companies, computer icons, buttons on websites, etc. Instead of storing an array of pixels, the file holds the start and direction/length of the line (i.e. a vector in math), as well as other information about it. This allows for storing these graphics in a much smaller manner than pixel arrays.
Inkscape has great tools for creating all kinds of graphics. It can do anything from full-page layouts for a publication (though there are probably better tools for that) all the way down to the favicon for a website. The “TK” image that you see on your browser tab for my blog was made in Inkscape!
Another neat feature is the ability to edit PDF files. Not just the ones with nice spaces to type stuff in, any PDF file. I’ve used it when I need to apply my signature and mail it back, but the file doesn’t have that ability and I don’t have a printer/scanner around. Open the file, draw my “signature” on, save, and e-mail off.
FLOSSing for lent 11/40