If configuring apt to dynamically use the closest mirrors on the internet just isn't fast enough, you can deploy your own mirror on your local network, which will dramatically improve the performance of updates and installations for other computers on your network. This is particularly useful if you have automatic KVM guest installations as I am. These tutorials will set you up so that you have an ubuntu mirror that is accessible through the web (http). You do not have to have your mirror accessible this way and FTP/NAS are good alternatives, but I chose http because it's common and easy.
Ubuntu users can use two different methods for setting up an ubuntu mirror, please pick one: