The USPTO issued updated guidance on Patent Subject Matter Eligibility (i.e. things you can get a patent for in the US) at the end of July.
The materials are fairly dense and help address some of the criticisms raised by applicants. Further explanations of the approach are provided as well as an expanded list of examples.
Reading between the lines, it appears the USPTO is moving towards a position that is harmonised with European, Chinese and UK approaches on excluded subject matter.
Having a relatively simple mind, I found the following page from the guidance summary useful.
IP Chimp 