Dev4PSP release PSPMSN Beta. You should think : Stupid, it's already developed.
But this uses a new version of Web Messenger.
This can be used on every firmware above 2.70. and also on PSP Slim.
You need to start it in the Webrowser.
This is not developed by me (Noob2PSP) but by Dev4PSP.
Srry no screenshot
Dev4PSP's Site : HERE