A couple of days ago I installed Lorentz, a beta version of Firefox. Lorentz is virtually identical to Firefox 3.6.3, except that it incorporates part of the work of the Electrolysis team. Their “Out-of-process plugins”-code lets Firefox-plugins (on Windows & Linux, they’re still working on Mac OSX according to the release notes) run in a separate process from the browser, meaning Flash (but also Silverlight or Quicktime) can’t crash Firefox any more.
This feature actually is long overdue, a substantial amount of Firefox crashes are indeed caused by Flash failing and Mozilla’s competitors (MS IE, Apple Safari and Google Chrome) already have similar (or even more exhaustive) crash-protection.
Once you’ve installed Lorentz (or Chrome or IE8 or Safari off course) you can safely visit http://flashcrash.dempsky.org/, which exploits a bug that was reported 19 months ago and which may still cause the most recent Flash-version (10.0.45.2) to crash. And if flashcrash doesn’t bring up the plugin-crash-dialog, you can always kill the “mozilla-runtime” process that hosts the plugins, just for kicks!