Beryl is now included in the Fedora Extras repository (which is available via a checkbox in the Fedora Core 6 installer)
You can install it with yum or pirut, just make sure you do it as root. The easiest way is to install a meta package, which will install all other needed files through dependencies.
You can install the meta packages with these commands in a terminal window:
yum install beryl-kde
yum install beryl-gnome
depending on if your desktop environment is GNOME or KDE.