http://www.macromedia.com/shockwave/download/download.cgi?P1_Prod_Version=ShockwaveFlash
As root, install it with:
tar -zxf install_flash_player_6_linux.tar.gz
cd install_flash_player_6_linux
./flashplayer-installer
You might need to specify your specific mozilla location. If you are running a default RedHat 8 installation, it is /usr/lib/mozilla-1.0.1
Enjoy,
Julian