Pagetest web page performance test is a great tool for doing what Firebug does but not in your browser. Pagetest can do repeated tests to iron out any outliers. An alternative is Pingdom tools which has some nifty sorting functions but is generally the same thing.
So I ran the homepage of my website on it and concluded that: Wow! Half the time is spent on DNS lookup!
The server it sits on is located here in London, UK and the Pagetest test was made from a server also here in the UK. Needless to say, I was disappointed. Is there anything I can do about that? I've spent so much time configuring Squid, Varnish and Nginx and yet the biggest chunk is DNS lookup.
In a pseudo-optimistic fashion I'm hoping it's because I've made the site so fast that this is what's left when you've done all you can do. I'm hoping to learn some more about this "dilemma" without having to read any lengthy manuals. Pointers welcomed.