I used to use Read it later, but it was really buggy; it had a habit of overwriting saved pages so the page would have one title but a different URL. The developers were aware of the problem but seemed to be having problems fixing it. I highly recommend Taboo however, it's a similar plugin I found later that also has an excellent mechanism for showing all the pages in your queue: https://addons.mozilla.org/en-US/firefox/addon/5756
