I am a newcomer to Jekyll, I am porting my site from Drupal, and found that I needed to get an overview of the pages, posts, collections, etc. as well as categories and keywords.
Inspired by PHP’s phpinfo() function, I hacked together a page called jekyllinfo.html that lists a whole bunch of details about the site, and about the content. Apart from this file, there’s a CSS style sheet and a layout.
The idea is that you can drop them in your project while you are developing it, it will give you a page you can navigate to to check the detailed info about your site. (The idea was also for me to learn about what parameters Jekylll makes available 
).
Check out the GitHub project, and feel free to contribute! I’m sure lots of improvements could be made.