OmniGraffle was recently upgraded to version 4.0. This is one of my preferit software for drawing. It resemble the beauty of CorelDraw but still not so powerful. Unfortunately Corel has decided that the mac users are not enough to justify development on this platform whereas the guys at OmniGroup are making big steps ahead. This new version has lots of new functionalities: SVG support, Bezier, Visio XML schema, etc. Definitely a must have starting at 50 bucks.