Via Oren Hurvitz's blog comes an interesting summary of two presentations that LinkedIn's engineers gave at the JavaOne 2008 conference. I've embedded the presentations below. The first goes into their architecture:
The second one deals more with their use of Java and agile practices:
It's great seeing details like this as it helps bring the rest of the industry up to date with how the largest websites in the world are actually handling the problems of performance and scalability. These are great for Microsofties to read too as the lessons learned apply just as well to .NET projects as Java ones.