Vienna is an offline reader for CIX that runs on Mac OS/X. originally written by Steve Palmer, it is now maintained by Christine Caulfield
If you don't know what cix is, you don't need it. If you do, (and use a mac) then download a copy.
And don't forget to join the cix:vienna conference to get support and news on updates.
Get Vienna at Fast, secure and Free Open Source software downloads