we just released our TinyMCE Widget plugin, that adds a WYSIWYG widget based on the standard TinyMCE WordPress visual editor. It is intended to overcome the limitations of the default WordPress text widget, so that you can visually add rich text contents to your sidebars.
Please give it a try and send us some feedback, if you want.
P.S. This is an alternative to the current version of "Wysiwyg Widgets" plugin, which is not working well at the moment.