Reduce the amount of arithmetic in the BlurEffect shader a bit. We did additions and subtractions with zero, which is sort of a waste on scalar architectures. Helps ever so slightly on the demo app on my NVidia card (3–4%).
Replace LAST_INPUT with INPUT.
Flesh out the blur code a little. It actually blurs now, although it is not as pretty as I would like it.
Add vertical blurring, and fix a bug where not all taps would be used.
Make the blur into a simple, Gaussian horizontal blur. Still not very good.
Support multiple render phases (with FBOs and all), and make a sample blur effect that uses it.