Asunder is a graphical audio CD ripper and encoder for Linux. You can use it to save tracks from an audio CD as WAV, MP3, Ogg, FLAC, Opus, WavPack, Musepack, AAC, or Monkey's Audio files. It has CDDB support and can create M3U playlists. It's independent of any desktop environment. It can rip and encode at the same time. It aims to make CD ripping as quick and easy as possible.
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.