Firefox only: (Windows) Firefox extension New Tab King adds a useful dashboard with recently used bookmarks and links to the Firefox blank tab page, so you can quickly access frequently used web sites.
Using the extension is simple enough—just use the Ctrl+T shortcut key, and the new tab page will show up with shortcuts to launch applications, the most used web sites and recently closed tabs—very similar to Google Chrome's new tab page, but in a list instead of a grid. Although you can customise the background image, there aren't a lot of other options to choose from—but it's an interesting extension that will hopefully get better over time.
New Tab King is a free download, works in Firefox for Windows only. If you'd rather have the Google Chrome new tab page in Firefox, you can do so by grabbing the latest version of the Google Toolbar for Firefox. Thanks, UnwinAspasia!