We've just launched a new site - diffify.com to help keep track of differences between R package versions.
Say you were using a particular version of a package in a project and now a new version is available. With Diffify you are easily able to check what has been changed in the new release. In particular, Diffify will provide you with information from the News file as well as changes in the dependencies, namespace and functions of the package.
For example, if you want to compare v1.0.5 with v1.0.9 of dplyr
This is very much version 0.0.1. Feel free to suggest features you would like to see in the future.