Except one is a bookmarking service that allows you to tag, it and the other is a reminder service... rereadit.co talks about this on the front page. Bookmarks

Except one is a bookmarking service that allows you to tag, it and the other is a reminder service... rereadit.co talks about this on the front page. Bookmarks you have to remember to go back and read it. This notifies you even if you forget to go to the bookmark.