Firefox only: If you're not using Firefox's Master Password to lock down your saved passwords, that's a mistake. Then again, the Master Password itself could be more secure and less annoying. The Master Password+ extension fixes its subject on both those fronts.
Once installed, your settings for the Master Password are greatly expanded in Firefox. You can add an auto-logout timer, as Master Password Timeout offers. Just as helpful is a settings tab that allows you to block all but the first Master Password prompt — I've personally run into multiple password prompts when I booted up Firefox, and while it's likely due to the tabs I was auto-opening, or the extension installed, it was as annoying as all get out.
You can add a Master Password link icon to your status bar, protect your Master options with a different password, and generally command how and when Firefox should lock itself down. Master Password+ is a free download for Firefox 3 and 4.