Tumblr developer Marco Arment opened up Instapaper, his latest side project. Think of it as a inbox for pages you want to pass up and read later. Instapaper gives you a bookmarklet to save the pages for retrieval when you have time to catch up.

Marco describes it as:

• You come across substantial news or blog articles that you want to read, but don’t have time at the moment.
• You need something to read while sitting on a bus, waiting in a line, or bored in front of a computer.

I think the thing I like most is the signup process. Put in your email address and you’re done. If you want a password, add one and you’re protected. Otherwise, there’s nothing else to do but fill it up with pages to read later.