The Postal Reading Challenge 2014 is hosted by The Indextrious Reader's blog.
It consists in read and review books with a postal theme (non-fiction on the subject of letter writing, collections of real letters, or epistolary fiction of any era). You review each one and link back to the challenge. You can sing up any time throughout 2104.
More details here and here the links related to the project.
Even if you don't sign up, you can discover a lot of interesting books!