Best solution : nspluginwrapper
Gnash looks promising, but has problems :

Lack of aliased fonts
Memory leaks cause small Flash panels to take over machine after a couple of dormant hours
No embedded video for video.google.com or youtube.com

http://gwenole.beauchesne.info/en/projects/nspluginwrapper/help#release_notes-rw-r–r– 1 platformedia users 53132 Dec 31 19:39 nspluginwrapper-0.9.91.2-1.x86_64.rpm-rw-r–r– 1 platformedia users 50362 Dec 31 19:39 nspluginwrapper-i386-0.9.91.2-1.x86_64.rpm
# rpm [...]