The site basically acts as “to-read” list. As you surf the net, you click on a bookmark (which you conveniently place in your links bar) and that page gets added to your “to-read” list; something that’s interesting but you don’t have time to spend on it right now.
One of the great things about the Net is its breadth of information; and one of the worst things about the Net is its breadth of things. While reading one article, you stumble upon another link to something that is applicable not to the subject at hand, but something else you’re doing… but now’s not the time to go down that road. So you click on your Instapaper bookmarklet and know that you can go back to it easily.
There’s no registration necessary. You don’t even have to set up a password (tho you probably should).
The service is free, but as they point out in their FAQ: “Instapaper isn€™t meant for permanent, long-term archival of everything you€™ve ever wanted to read. And while best efforts are made, your data€™s integrity is not 100% guaranteed here. This is for temporary storage of links you€™d like to read.”
I’ve found the site to be incredibly handy and thought I’d do my part to spread the word.