Not sure if this has been mentioned yet:
Adding Open DNS codes to your Network Preferences, should give good results in terms of speed-up as well as added security:
If you are using a single computer: Open System Preferences/Network. Double click on your connection type, or select it in the drop-down menu, and in the box marked 'DNS Servers' add the following two numbers:
208.67.222.222
208.67.220.220
(You can also enter them if you click on Advanced and then DNS)
Sometimes reversing the order of the DNS numbers can be beneficial in cases where there is a long delay before web pages start to load, and then suddenly load at normal speed:
http://support.apple.com/kb/TS2296
If your computer is part of a network: please refer to this page:
http://www.opendns.com/start/bestpractices/#yournetwork and follow the advice given.
You could also try these codes as well: 4.2.2.1 & 4.2.2.2
If you use a Router, make sure it has the latest firmware installed.