I just added GLSL shaders to the SDL OpenGL rendering implementation.
On my hardware this ends up being about a 200-400 FPS increase in testsprite2:
4259.55 frames per second
4552.88 frames per second
I also got a modest increase with testsprite, using the old SDL 1.2 API:
1329.16 frames per second
1354.20 frames per second
I also noticed there's not a single example of using shaders with SDL that has full source code, so I added one: