OldSchool Library for PSP is the best PSP library and has currently no serious competitor.

Changelog:
-Added: VFPU Math Library libpspmath version 4 by MrMr[iCE]
-Added: Remote control functions
-Added: Sony Browser (see the sample)
-Added: oslDrawStringf [oslDrawStringf(0, 0, "Test string %i", 1);]
-Added: adhoc functions (based on pspZorba's adhoc sample)
-Added: switched to libjpeg to load jpg
-Added: Switched to intraFont 0.31
-Added: Functions to delete a savedata or save with multi list (thanks to valantin)
-Fixed: debug console
-Fixed: minor bugs