Custom GLSL Filter for Viewport Is it possible to add my custom GLSL filter to 3d viewport? Like my custom SSAO or custom fog based on depth and normal passes.

I want to add my custom SSAO filter to a 3d viewport form here http://blenderartists.org/forum/showthread.php?234822-new-and-fast-SSAO
But this is only for BGE. But i would like to use it for ObjectMode.
You would have to modify Blender on the source-code level to inject custom screenspace shaders to the viewport. Something that requires a decent knowledge of C/C++ and Blender's codebase. 

But the latest build of Blender (since 2.73) actually has SSAO and DoF built into the viewport. You can try it out by downloading the daily build from http://builder.blender.org