I just wanted to mention that Adobe has released a native 64-bit version of their Flash plugin for web browsers today. I installed it for Firefox by going to this page, and clicking the “Download 64-bit Plugin for Linux” link. Before doing anything uninstall all flash plugins that you have on your system! For me, this was achieved by removing the nspluginwrapper and flashplugin-nonfree packages. Just extract the file you downloaded from the Adobe page; you will get a file called libflashplayer.so. Create a new directory called “plugins” in ~/.mozilla. Then, copy the libflashplayer.so file into ~/.mozilla/plugins, and restart Firefox. Done!
Even though it’s an alpha release, it seems to be working fine for sites like Youtube and CNN video, on my Xubuntu 64-bit system.