This Stream Spigot tool lets you read blogs (or anything else with an RSS or Atom feed) from the beginning. In addition to being useful for newly-discovered blogs with big archives, it also works well for topical "advent" blogs or if you want to learn something new.
Simply enter the URL of the blog or feed that you wish to play back, and (optionally) pick a start date and update frequency if you don't want to read it from the beginning. Once the playback is setup, you'll get an Atom feed URL that you can subscribe to.
Feed playback has begun. You can:
Subscribe to the playback feed
There was an error setting up feed playback. Details.