LiveQuartz is a simple and powerful free 64bit photo editor for Snow Leopard.
It is based on non destructive layers and filters.
The layers are at the left and the filters are at the right of the window.
To edit a photo, just drag it into the window (or layers' list) and it will be added as a new layer.
LiveQuartz handles Multi-Touch Trackpads.

Video demos here :
http://www.rhapsoft.com/?menu=livequartz_video

LiveQuartz has all the essential tools:
The drawing tools (brush, lines, rectangles, ovals), the duplication tool, the eraser tool, the new background eraser, the gradients, the layer moving arrow, the text tool, the CoreImage tool, the rectangle and lasso selections, the hand, and the magnifying glass.

LiveQuartz is localized in English, Simplified Chinese, Traditional Chinese, Danish, French, German, Italian, Japanese, Persian, Russian and Spanish.

LiveQuartz 1.8.4 remains available for Leopard users on LiveQuartz WebSite.