Extensions like ‘Speed Dial’ (https://addons.mozilla.org/en-US/firefox/addon/speed-dial) are already there to implement this feature in Firefox, but according to the latest article on wiki.mozilla.org (https://wiki.mozilla.org/Firefox/Features/New_Tab_Page), this feature is intended to be the simplest possible version of a new tab page. Following are the requirements for the New Tab Page:
Show a grid of top 9-16 sites when opening a new tab. Responsiveness of new tab shouldn’t appreciably decrease. It should be possible to remove sites that show up in the list. It should be possible to rearrange the list. It should be possible to manually add a new site to the list When opening a new tab using keyboard shortcuts, we should visually de-emphasize the grid. (Current direction: desaturate colors to black & white, fade in colors if mouse is being used).
You can read more about this news at source here. Interested users can download Firefox 9 nightly build (test build) at Mozilla’s ftp servers.