ISO Master is an easy to use GUI CD image editor for Linux, BSD, and Windows. Basically, you can use this program to extract files from an ISO, add files to an ISO, and create bootable ISOs, all in a graphical user interface. It can open both ISO and NRG files, but can only save as ISO. It is based on bkisofs, a library for reading, modifying, and writing ISO images.
Information regarding Project Releases and Project Resources. Note that the information here is a quote from Freecode.com page, and the downloads themselves may not be hosted on OSDN.