readbag is one of those incredibly simple and well-implemented services that puts a subtle but useful twist on a product in an already crowded space. The readbag bookmarking service (it's actually a Google App Engine application) provides the functionality to do one thing very well--bookmark pages that you want to read for later.

Now you might argue that you can use any social bookmarking service to do this, or something like Evernote. But what readbag does well is eliminates all the noise of social bookmarking, and gives you a nice mobile interface (generic mobile ui or IUI for iPhones) so that you can retrieve those articles you don't have time to read now. So when you're on a train maybe, or waiting in line somewhere, you can read them on your phone. The little twist is that it acts a bit like a to do list. Once you've followed a link from the readbag interface to one of those saved articles, it gets removed from the list, assuming that you've now you read it. You can unarchive links if you haven't read them yet.

This goes a long way towards making my iphone more useful as someone who is constantly finding blog entries and articles to read, but not being able to read them all when I'm at the computer. What would really work well for someone like me, who occasionally is out of reach of a cell tower signal, is an application that can create a text-only version, cached on my phone so that I can read those articles on the subway. Of course, if iPhone's Safari ever does offline reading this wouldn't be an issue.

This is a very well implemented product design for a service that wants to be simple. Check it out.