I searched the site and didn't see this very useful extension mentioned anywhere.
Snap Links allows users to easily open multiple links in new tabs by drawing a box around them. Links can also be opened in new windows, new tabs on a new window, copied to clipboard, bookmarked or downloaded. Quite useful when you want to open a bunch of links.
Snap Links:
https://addons.mozilla.org/en-US/firefox/addon/4336