Synfig: for cross-platform 2D vector animation (Adobe Flash alternative) at http://www.synfig.org
Scribus: for desktop publishing (Adobe InDesign alternative) at http://www.scribus.net
FlashDevelop: for ActionScript development (Adobe Flash Builder alternative) at http://www.flashdevelop.org/
MyPaint: for intuitive full screen digital painting (Autodesk Sketchbook alternative) at http://mypaint.intilinux.com/