web_accelerator

I am trying understand some open web accelerator, and as of now going through the data from http://en.wikipedia.org/wiki/Web_accelerator  and found following is the order: if I have to chose a open web accelerator:

1. Varnish: http://en.wikipedia.org/wiki/Varnish_(software)

2. Nginx: http://en.wikipedia.org/wiki/Nginx

3. Squid: http://en.wikipedia.org/wiki/Squid_(software)
4. trafficServer: http://trafficserver.apache.org/  [ ATS: Apache Traffic Server ]