PS3 CEX to DEX 4.20 download

So this method not for beginners at all so do not attempt this is you are not totally sure what you are doing.  There is a massive risk of bricking your console during the conversion if you make a mistake

http://www.mediafire.com/?9dqd0x3vl24384z

4.20 Custom Firmware is released | PS3 jailbreak upto 4.21

There has been some new developements in the PS3 scene with the CEX to DEX PS3 conversion method being leaked very quickly after the PS3 Jailbreak 4.20 custom firmware that will also install to a 4.21 PS3.  While these two may seem related they are entirely different systems with different end results so you must decide for yourself which direction you will take.
Regular users just wanting to play backups online will need to follow the PS3 Jailbreak scene or even the dongle scene but for developers and people wanting to play with the hardware but forgo online game play then the DEX method is very much of interest.