This is the New Light Custom Firmware (LCFW) 6.60ME 1.6 for PSP 2000v2, 3000 and Go models. There is also a CFW for PSP 1000 and 2000 models and the link will be posted below.
After downloading the file for whatever PSP model you have, extract the files to your desktop or open them using an extraction program. You will see the Release 6.60lME folder and then open it. Inside will be the leda folder and the UPDATE folder.
Step 1: Attach the PSP via USB and open the Memory Stick (MS) and on the root of the MS create a folder, If you haven't already, called "seplugins" (NO QUOTES) and open it. Open the Leda folder in the extracted files and you will see a leda.prx and a readme.txt. Take the leda.prx and drag that into the seplugins folder. If you have a previous one in there, replace it with the new one. Now on the PSP seplugins folder create a new txt document called "game" and open that and type in it "ms0:/seplugins/leda.prx 1" or if PSP Go type "ef0:/seplugins/leda.prx 1" and exit and save.
Step 2: Go back to the MS root on the PSP and open the the PSP folder and then the GAME folder and from the extracted files take the Launcher folder and the Installer folder and copy that into ms0:/PSP/GAME and thats it.
NOTE: If you are updating from a lower CFW than 6.60, Download the OFW 6.60.PBP and place that in the UPDATE folder inside ms0:/PSP/GAME.
Step 3: Exit everything and now run the installer from the XMB and your done