FastBrowz

FastBrowz is a must-have plugin for users who spend time on Hacker News and Reddit.

With the add-on installed, you can hover over any link on the Reddit or Hacker news pages and it will show you a full preview of the target web page in an inline window without leaving the current page.

You can also hover over the comments link and the preview window will show the top rated comments for that thread.

The extensions saves you from having tons of tabs in your browser but it may not work with sites like the New York Times or Github link as these sites include the frame breaking code disallowing other sites to embed them inside IFRAMEs.