There are number of applications that you wouldn't be able to move to SD Card as a default and APP2SD will not show these as moveable applications. However there are some less critical apps that you are able to move to SD Card with a tweak.
You will have to install Android SDK and have a working shell using USB Debugging connectivity. Once you have this installed, you will probably require some USB Drivers for your model of phone which will allow windows to recognise the phone. After you have all this sorted you will have to issue couple of commands in ADB Shell which will enable some existing apps to be moved to SD Card and will also set the location for new apps to SD Card.
# adb shell
# pm setInstallLocation 2
However in order to reverse this settings so that new applications are installed in system ram you will have to do following.
# adb shell
# pm setInstallLocation 0