TweakDISPLAY allows you to alter your PSP display settings.

Changes:

-> VshMenu Now works.
-> NEW EFFECT: Added Flip Mode 30 Stable; No memory leaks, no crashes, No screen artifacts, however 30fps.
(Note: Once you go over onto the experimental mode, the PSP is may crash at any time, so, going back to this effect wont help.)
-> SPEED BOOST for “Brightness Boost” effect: +15-20fps. (Keys: TRIANGLE+SQUARE + Analog Up/Down)
-> SPEED BOOST for “Contrast Boost” effect: +15-20fps
-> Bug fix: In Flip Mode, When the effect was toggled to off, the keys werenot mapped back correctly; Fixed.
-> Changed controls: LTRIGGER + RTRIGGER = Toggle current Effect.
-> Changed controls: Now uses TRIANGLE + LTRIGGER/RTRIGGER to change effect; the controls are “invisible”, wont affect the what’s happening on screen.
-> Snappier responce when Brigtness is adjusted in brightness mode.
-> Miscellaneous code cleanups.

http://forums.qj.net/psp-development-forum/148788-release-tweakdisplay-v1-0-1151-maintenance-release-your-psp-worth-itself-x-23-a.html