I've recently seen various people blog about how to speed up firefox by changing the settings in about:config (or user.js), and it reminded me of my old painfilled days with internet explorer over a 33kbps dialup. Back then I found this link for Internet Explorer, which showed how to increase the number of connections and pull down more streams to the browser.
At the time, I was impressed that Microsoft had (conveniently) put the value into the registry, allowing it to be increased, but it looks to have been trumped by the degree of configuration that can be safely done via javascript in Firefox. You can find an excellent breakdown of tweaks per computer/connection combination here , or go straight to the source for the granddaddy of all tuning posts.