You can do it this way, without using Google Drive API:
- Make the folder public
- Copy the folder ID from the URL
- Append it to https://googledrive.com/host/ e.g. https://googledrive.com/host/0BzEbtMoF6IXbaVN2Qmx1em9qS0k/
You will get a directory index with all files listed and if the (sub)folder contains an index.html file, it will be rendered instead.
To get the JSON or XML file list, use YQL.