Uncharted Desert Isle

You can grab webpages, feeds, articles, links, whatever, gather them up in a book (great for those multi-page livejournal stories). You can select text to add, edit the text, rearrange the pages if you screw up the order of them, name it whatever you like (under save as option), and even add metadata.
Note If you want it to save for mobi, GrabMyBooks needs calibre to convert it.
Go to add-ons at firefox to find it, or http://www.grabmybooks.com/
I LOVE IT.