One of the things I immediately noticed about GNOME 3 is that the keyboard break feature, formerly a default option in GNOME 2's normal Keyboard Preferences setting dialog, has been removed. For RSI-aware geeks like myself, that is a big sadface. Fortunately, it's easy to re-enable, but exactly how to do it is a bit obscure, so I'm documenting for posterity.
There are plenty of Linux-native typing break software packages, but if you want GNOME-integrated typing breaks, the relevant piece of software is called drwright, and that link points you right to the most recent source (as of July 2011; if it's much later, check the parent directory to see if there are any later versions). It's packaged in most major distros, including Fedora, so a simple sudo yum install drwright will do the trick.
Once you install it, typing breaks are configurable via the System Settings menu (throw your mouse into the top left hot-corner, then type "system" to find the menu).
You'll see a new Typing Break option.
If you click on that, you're back to the old familiar Typing Break dialog.
That's it - modularity for the win.
(Thanks to Sebastian for digging back through his history for the proper package name; I initially thought typing breaks were Gone Forever from GNOME 3 and was about to evaluate a slew of non-GNOME options.)