A Ruby file parser/interpreter/preprocessor that comments lines of code based on conditions at the time the file is required. Very handy to implement debugging logs and code that has to be commented (not just dynamically switched off).
A GNOME WYSIWYG HTML/XHTML editor written in Ruby (Ruby-Gtk2) The overriding plan is to support freeform editing of sourcecode that the WYSIWYG editor can detect without changing the code layout. The program also supports plugins to extend the interface
Create a text editor for computer programmers. Use ruby as underlying system and write core code in C. Support at least inline debugging as well as common features such as colored keywords.