BGP

Great article:
http://www.netcraftsmen.net/resources/archived-articles/382.html

UPDATE:  It appears netcraftsmen.net is no longer there!  http://web.archive.org/web/20121219075610/http://www.netcraftsmen.net/resources/archived-articles/382.html

This entire site looks very good.

The Cable Guy: Strong and Weak Host Models

The Cable Guy: Strong and Weak Host Models: Strong and Weak Host Models
Multihomed server configuration