I would say LYNX (text based browser).

It has no pictures to download or anything as everything is strictly text. Much of what makes downloads lag is pictures and videos. Without that, it's just letters and hence everything goes at warp speed. Problem is, it isn't in the least bit pretty.

In my personal experience, Firefox 3.5 is just about as fast as Chrome. But I also have a "infinite" bandwidth pipe so it's pure rendering speed that seems about equal. IE and Opera (alpha) both were noticeably slower. However, give Firefox prealpha 3.7 a shot. It's the fastest I've ever seen even vs. Chrome.

Oh yeah and disable extensions compatibility checking in the about:config (google for more details), so most of your extensions will still work even though they're not "officially" supposed to.