Here to report that the post processing builds are now working correctly on the latest radeon cards (I use an HD 4870). Absolutely no problems to report, except for unclear instructions on how to use the post processing table. Most values just give me an incomprehensible cube-arranged mess of speckles...
Some post processing filters to think about are gamma and hue controls, posterization, cell shading (outlines and such - this would be more difficult to implement), screen space warping, guassian blur, ghosting (basically a crude motion blur that you'd see when injured in, say, a Call of Duty game), and color inversion. Some of these could be combined to, for example, have a first-person view of entering a warpout when you end your mission.
Something that would be extremely useful is the ability for conditional post processing - I'd like to see some full-screen distortion and contrast/saturation fudging when hit by an EMP bomb, for instance. Being in the wake of a shockwave would also be grounds for possibly some light distortion and a gamma increase. A subspace mission would need some overbright post processing, maybe some ramped up saturation and contrast, and an intense but tight bloom effect. A nebula mission would need a less intense bloom, but the glow would be very large, giving a greater impression of a murky soup that disperses light.
Also, the mjolnir blockade mission is really fun with bloom activated...