I had some issues with Adobe Flash crashing very often using the latest Firefox 4 so I've searched for a way to fix this and found a topic on AskUbuntu which says to use Chrome's Flash plugin in Chromium so I though - why not do it for Firefox? - and it's actually working quite well for now.
Chrome uses a built-in Adobe Flash plugin which seems to work better then the regular Flash. But there's a catch: you must install Chrome (and keep it updated if you want further Flash updates) even if you don't use it.
Use the built-in Chrome Flash plugin in Firefox
1. Download and install Google Chrome (I for one prefer the unstable branch but I guess any version will do)
2. Open a terminal and copy / paste the following commands:
mkdir -p ~/.mozilla/plugins ln -s /opt/google/chrome/libgcflashplayer.so ~/.mozilla/plugins/
3. Restart Firefox.
The exact same instructions above also work for Chromium (yes, using the ~/.mozilla/plugins/ folder even though it's for Chromium).
Note: I've tested this with the latest Firefox 4 32bit only (and Chromium 32bit)! It should work with older Firefox versions too though.
What other "tricks" do you use to improve Flash performance under Linux? Let us know in the comments!