Well, in Instapaper you can read the articles you saved in the original format or striped down, but always with the images of the article. It's only the ads, header and navigation information that is striped down. You click on the link to see the original version and on the Text button to see the stripped version.
Additionally Instapaper also has folders but there is a bookmarklet for every folder, so I don't know if you'll be able to save in a way users can choose the folder.
A really nice feature instapaper has is the possibility to deliver the read later pages you saved directly into your kindle (or any device with a kindle application).
Another nice feature is that users can link with their readability pro accounts and with that reward the authors of the articles they save and read later.
(I was going to post images of Instapaper here but I don't have enough reputation to do so)