Firefox 3 Beta only: If you’ve taken the plunge into testing the brand new Firefox 3 beta but your favorite extensions are disabled, that’s because developers haven’t updated them and may not be providing secure updates yet. If you’re an impatient risk-taker who needs your extensions back NOW, here’s a cheat that may get them to work. Big Honking Warning: Only do this if you’re willing to deal with possible bleeding edge extension bugs and security risks!

• Type about:config into Firefox’s address bar and click the “I’ll be careful, I promise!” button.
• Right-click anywhere. Choose New>Boolean. Make the name of your new config value extensions.checkCompatibility and set it to false.
• Make another new boolean pair called extensions.checkUpdateSecurity and set the value to false.
• Restart Firefox.

All goes well, and any extensions that aren’t yet officially Firefox 3 Beta 3 compatible and don’t have secure updates (like Better Gmail and friends) will be enabled. Final warning: These changes may lead to unexpected wacky behavior. Proceed at your own risk! Thanks, BugMeNot21!