You should not runn load/stress testsing benchmarks on the same machine that you run the target web server on.

apache bench

httperf

Generates workloads to test HTTP servers.

• Think time (mimic user behaviour)
• url generation
• bust support
• GET/POST queries in a session file

  httperf -hog -server=127.0.0.1 -port=3000 -wsess=100,5,4 -rate=2 -timeout=5

httpload

  httpload -rate 10 -seconds 60 url.txt

trample

  Trample.configure do
    concurrency 5
    iterations 10
    get "127.0.0.1:3000"
    get "127.0.0.1:3000/login"
    login do
      post "127.0.0.1:3000/users/sign_in" do
        {:user_email => 'blah@blah.com', :user_password => "secret"}
      end
    end
  end

  trample start filename.rb

New Relic

Great for web application performance monitoring and management.