Instructions
Download and install one of the many free PS3 video converters available online, since the console can't handle flash video natively. Click the "Add" or "Browse" buttons once installed and select the FLV file. Use the "Options" menu to adjust the quality of your video and click "Convert" to create a PS3 compatible video.
Place your FLV in a folder on your desktop and download PS3 Media Server. This free program converts video on the fly and sends it to your PS3 over a local network. Once PS3 Media Server is installed and running, turn on your PS3 and select "Search for Media Servers" on the PS3. Once your PS3 has recognized your computer, browse to your file and play it.
Upload your FLV to a third-party video hosting site like YouTube or Metacafe. While the PS3 isn't able to play FLV files from its main menu, it can stream FLV files as easily as any modern browser. Open the PS3 browser, press "Start," input the address of your files, and press "Start" again to access them.