Faststone Image Viewer For Mac
Faststone Image Resizer
Although you can use Picasa to view most RAW files, it has only very limited facilities for editing them. An excellent alternative viewer is IrfanView.
Fast sum alternatives for mac. This is available for Mac and is free. It will open almost any known graphics format files. You might also consider GIMP. This too is free and is available for Mac. It is almost as comprehensive as PS but not very user friendly! Although its plug in UFRaw will handle most RAW files, it is never kept quite as up to date as PS and so might not be usable with the very latest camera files.
Faststone Image Viewer For Mac
An easy alternative to consider is Adobe's free DNG Converter. This converts your RAW files into the DNG format which can then be manipulated in most independent RAW programs, but not in most camera manufacturer's own programs. It can be kept very up to date too. The DNG format will give you access to many other Mac alternative programs.