Simple Rich Text Widget is a WordPress plugin by Keith P. Graham that adds formatted HTML to sidebars.
The author says: “I needed a very simple way to add formatted text to the sidebar on my blog. I used this simple plugin along with an old rich text javascript file that I wrote and wound up with this. It works on my blogs, but the javascript may not work if oyu are using anything but the default admin pages in WordPress. The rich text edit area on the admin screen is wider that the admin page allows so I have put it in a scrollable div. I have been testing with FireFox 10 and IE8. I hope that other browsers work. In any case, the widget display should be well formed and standard HTML and display pretty much the same in all browsers.”
Download: http://wordpress.org/extend/plugins/simple-rich-text-widget/
