Just load them in web browser and copy cache files.
In windows vista/7, the files are stored in format:
C:\Users\<username>\Appdata\Local\Temp\fla*.tmp
you will need "Hobocopy" to copy them, to bypass windows "File in use" error.
cmd.exe hobocopy example:
C:\> Hobocopy %TEMP% C:\hobocopy-temp
-- output --
C:\> copy C:\Hobocopy-temp\fla0Ef3.tmp C:\where\ever\my_video.flv
On linux, be sure to use opera(firefox cache on linux is.. odd) and use command:
$ find ~/.opera/cache -type f -size +3072k | xargs ls -lh
Will print your vids. In both cases just copy, rename the files to .flv, then convert to format of choice. I just keep 'em in flv and play using VLC.