The idea is simple:
When one browses the web, she often comes across lengthy articles that she would like to read (or videos that she would like to view). Often she doesn't have time to read them at the time that she finds them. She probably leaves them open in a tab in her web browser, which is an okay solution until it starts slowing down her computer, or her browser crashes, or it gets buried under a pile of other tabs.
That's where Listomat comes in. Now, she clicks a single button in her browser's favorites bar, and the page is automatically added to her Listomat. Later, when she has some time to kill, or she's in the mood for some reading, she can come back to her Listomat.
An active installation of Listomat can be found here. Listomat is a Free Software (GPL) project started by Parker Phinney. It hopes to become a larger Free Software project and a popular Free Network Service. Drop Parker an email if you'd like to lend a hand. For now, you can grab the source here.