Oink - Oink is a Rails plugin and log parser to help narrow down the source(s) of increased memory usage in rails applications.
VisualVM - VisualVM is a visual tool integrating several commandline JDK tools and lightweight profiling...
Munin - PnP networked resource monitoring tool that can help to answer the what just happened to kill our performance
JProfiler - JProfiler is the leading Java Profiler for profiling on the JVM. JProfiler's intuitive UI helps you resolve performance bottlenecks, pin down memory leaks and understand threading issues.
Derailed Benchmarks - Derailed Benchmarks is a benchmarking tool for Rails.
Eclipse Memory Analyzer - The Eclipse Foundation - home to a global community, the Eclipse IDE, Jakarta EE and over 350 open source projects, including runtimes, tools and frameworks.