devparis

It will show all server information in an admin page.

YLD Server Information

It will show all server information in an admin page.

cleanscript

A very simple plugin that provides information about the Custom Page Templates available in the theme: What they are, which are not used and where the used ones are used, selectively.
Main features: 
Available page templates list 
Unused page templates list 
List of page templates with checkboxes that output when submitted the links where they are used

Cleanscript – Page Templates Info

Find information about your page templates. What they are, which are not used and where the used ones are used, selectively.

YLD Server Information vs Cleanscript – Page Templates Info