At ultradns.com or on comwired.com you can select multiple A records depending on location;
x.com (United States) 126.96.36.199 x.com (Europe) 188.8.131.52
So requests are routed based on proximity/where they come from.
You can do that as many times as you like, which is a great service for our distributed application needs.
However, we want to manage this on our own servers. Do you know any linux package that does this ?