Firefox Useful New Tab Page addon is out of experimental hosting at Mozilla now and is available here; https://addons.mozilla.org/en-US/firefox/addon/useful-new-tab-page/
I also placed the source code for it on Github here: https://github.com/timtocci/Firefox-Useful-New-Tab-Page in case anyone wants to check out the source code.
I gave it four stars on addons.mozilla.org.
I like it.
I have one suggestion; collapse consecutive identical titles in the Recently Visited column. I use Boing Boing a lot and jump around the BBS pages so I end up with a lot of identical titles in that column. It might be reasonable to have only the most recent one of each block of identical titles. Or you could hide the duplicates and provide a button to reveal them.