FreeDMG
Do you need to create DMG images on the fly? FreeDMG is a great little app that does exactly that, and as its name implies, it is entirely free. This newly released version adds "adjustable compression levels in preferences (with UDZO format only), the option to overwrite exising files,
and an option to quit after imaging on dock drop launch." You can also password protect the images quickly and easily. Check it out.