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Much thanks to my friend Matt for pointing this out to me. This is a method to hook up a USB device to your Play Station 3 and play .AVI movies on your TV. I have not tested out other file formats, but I suspect any MPEG format will work. Feel free to ask questions and I'll try to find the answer.
You can also use practically this same method to view pictures and listen to audio.
*****As asked below, if your USB device does not show up, ensure that it is formatted in FAT32, not NTFS.*****
*****Also as commented below by DaveSimonH:
"To prevent having to press Triangle then select "show all items", create a folder on the root of HDD/USB named VIDEO, and then stick all your movies in there with whatever subdirectories you want. Then you can open it up like any other video folder on the PS3"
Thanks for the great tip, DaveSimonH*****