I was recently introduced to a tool to help with my web development by giving me some benchmark results. This will allow you to emulate multiple users accessing your site and to verify that the load times are acceptable.
ApacheBench, which is bundled with the standard distribution of Apache will let you do some pretty cool benchmarking tasks. And to sweeten the deal if your using a Mac the tools are already installed for you.
Here is an example of its use:
Open a terminal
Applications -> Utilities -> Terminal
$ ab -n 100 -c 10 http://www.google.com/
This will execute 100 HTTP GET requests, using 10 threads (10 requests per thread) to the specified URL, in this example,