The folks at Mozilla have released a new version of the Firefox Web browser, version 3.6.4, for all platforms: Mac OS X, Linux, and Windows. This version incorporates a new feature, intended to provide better resilience in the (unfortunately frequent) cases where a plugin, such as Flash or Silverlight, crashes. These plugins will now be run in a “sandbox”, as a separate process. If the plugin hangs or crashes, you will be able to reload the page to try again; if the plugin is causing other problems, its process can be killed without terminating the browsing session. (I have been using this feature in a beta build of Firefox for several weeks, and it works well.) The new version also incorporates fixes for seven security vulnerabilities, and some miscellaneous other bugs. Further information is in the Release Notes.
You can get the new version via the built-in update mechanism (main menu: Help / Check for Updates); this requires that you have administrative privileges. Alternatively, installation binaries for all platforms, in 70+ languages, are available from the download page.