ControlJS is a JavaScript module for making scripts load faster.

get notices about when you should use eager loading (n+1 queries) and when you've got unused eager loaded data

jQuery plugin by John Resig to deep profile your web app and get a list of time spent per function. Just used this to profile something and it worked great.

A Framework and ORM agnostic Model / record attribute tracker to ensure production Ruby applications only fetch the database content needed to minimize wire traffic and reduce conversion overheads to native Ruby types.

helpful

nice, free rails app monitoring

Httperf is a tool for measuring web server performance. It provides a flexible facility for generating various HTTP workloads and for measuring server performance.