I thought I should share this with those who recently purchased a PS3 Slim this past Tuesday.
To play a video or movie on a PS3 besides a disc just save the file on a usb device, memory stick or external hard drive, and simply create the following directory at the root of the device:
Then just simply copy your video file preferably an .mp4 file to this new directory. Connect your usb device to the PS3 via one of the two usb ports and navigate to videos and then down to your usb device, select this icon.
You should then see an icon for your mp4 file, select it and it should play. Enjoy!