Can you point me to an overview of clustering support in GlassFish v2?

This article describes the clustering capabilities of GlassFish v2 and helps you get started deploying your application to a GlassFish cluster. Also check out the podcast about clustering, one of many GlassFish podcasts that provide interviews and news from the GlassFish community.

Other good resources include the Aquarium blog, which is a great way to stay on top of GlassFish v2. A detailed clustering write-up and FAQ by Nazrul can also be found here.