Improve the real or perceived speed of the site, or monitor performance metrics.
Aggregation Per Role is a module which allows users to debug CSS and Js with their role without affecting other role's performance.
This module has been abandoned in favor of a newer project of mine:
Simple Module to view PHP OPcache statistics and configuration. Allows to reset OPcache from admin interface and via PURGE and POST request remotely.
The goal of this module is to present users with the best possible image derivative (thumbnail, crop, size, etc.) depending on the actual client side context.