@el_cravito: I've had confirmation from the FreeDMG developer that a Leopard update is still coming, as the current 0.5.5b doesn't reliably support Leopard.

Yes.. I agree. EasyDMG works great and it's very simple to use. But it cannot do encrypted disk images.
There's a free alternative that is able to create encrypted DMG files: it's called FreeDMG. And it also works with Leopard.
http://osx.iusethis.com/app/freedmg
Disk Utility, that comes with Mac OS X, can also do encrypted disk images.

Works great...simple and does what it's supposed to do. Leopard compatible, too!