MasterView™ is a ruby/rails optimized HTML/XHTML friendly template engine. It is designed to use the full power and productivity of rails including layouts, partials, and rails html helpers while still being editable/styleable in a WYSIWYG HTML editor.

An ajaxified interface to maintain bunches of data in active record.  Good for admin and other tasks.  This looks like a good start for displaying and editing big chunks of data.  It has a nice javascript interface for editing in table form rather than one record at a time. 

Snippets for various ruby solutions

These are Ruby addons, not rails addons.  They extend the standard ruby classes and add some new ones.

A Rails extension that adds permissions, templates, a markup language, themes, and is built with ajax and javascript where useful.

Tools for applying javascript to RoR apps.