Well, this is one of the few places where a Mac & Windows can co-exist 
No flame wars guyz.
A Collection of the Best Free and Open Source Software from Mohawke contains both Windows & Mac software, mostly free. There is a brief description of the software too.
Nice for a casual view. A definite look though.
Somethings I found interesting & new...
ArtRage, a Natural Painting Application, like Painter, worth the download!
Both Win & Mac
Delineate, Raster to Vector coverter. Nice.
Deep Paint 2.0, offers a realistic painting experience for digital artists and graphics professionals. Deep Paint intergrates stroke-by-stroke artistic photo-cloning, fully editable brush and canvas settings, and paint functionality for realistic and stunning paint effects. Experience thickly textured oils, bold acrylics, and dramatic watercolors. Deep paint simplifies your artistic workflow as a Photoshop plug-in or standalone application, with special support for the Wacom Intuos or compatible pressure sensitive pad.
Doubletype, Font creation application.
Hugin - Panorama Tools, Make panoramic photos out of normal images.
Best Free and Open Source Software Collection
Re: Best Free and Open Source Software Collection
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