Saving FLV videos from browser's cache

Rather than installing plug-ins in firefox for downloading videos you can easily copy the viewed video from your firefox's cache. This is how you do it. This is specific to Linux.

Find the location of your browser's cache on the disk 

Ideally it should be located at /home/YOUR-HOME-DIR/.mozilla/firefox/YOUR_PROFILE/Cache

Use the file command to find the flv/flash files in the cache

Sort them by time to search through them easily
   ls -t arranges the output with respect to the modification time

   # ls -t | xargs file | grep -i flash
   A9E2629Ed01: Macromedia Flash Video
   D69CD130d01: Macromedia Flash data (compressed), version 10
   792592C0d01: Macromedia Flash Video
   DBABC51Ed01: Macromedia Flash data (compressed), version 10
   21DF1037d01: Macromedia Flash data (compressed), version 10
   43258D0Fd01: Macromedia Flash data (compressed), version 8
   17DA266Fd01: Macromedia Flash data (compressed), version 7 

By some hit and trial you will be able to find the file you want to save
    Play the files using any video player which supports flv videos

    # vlc A9E2629Ed01 &

Use mv command to rename and move the file to the desired location

   # mv A9E2629Ed01 ~/Videos/rise_up.flv

You are done :-)