GNU Emacs 18.58 is the current version. Fixes from 18.57 include better mail address parsing, an X visual bell speedup, a call-process enhancement, a regexp matching change, the ability to apply a numeric argument to a self-inserting digit, getting X resource values from the RESOURCE_MANAGER property, more reliable shell mode job control, and a change to copy-keymap. Also, support has been added for many new system types. Fixes from 18.55 include the removal of arbitrary limits on the undo facility.
According to the January 1992 GNU's Bulletin, "Emacs 18 maintenance continues for simple bug fixes.".
To visit a file with information about what has changed in recent versions, type "C-h n".