there are now lobbys for mw3
you can host them yourself if you have ( jailbroken ps3 )
-3.55 PS3 with PSN access (follow this tutorial)
-The update PKG provided in the download section below
-The EBOOT.BIN provided in the download section below
-USB stick for installing the PKG
just pm me for the link if you can also host for me (A) ( I am not allowed to post these links here )