Anil Saldhana just pointed out this article about how you can use JBoss Identity Management to provide SSO capabilities to your Seam application. It discusses a couple of approaches.
One of the medium priority targets for Seam 3 is to provide better support for JBoss Identity Management out of the box.
Tags: Seam News
The article pointed out here, describes ways to connect Seam to SAMLv2 based identity providers, using the Tomcat valves that are available in the alpha versions of JBoss Identity.
The first beta version of JBoss Identity, to be released soon, contains built-in Seam support, which is easier to configure and which integrates better with the security features of Seam.
See this wiki article.