SiteMesh can be found at http://www.opensymphony.com/sitemesh
Integrating WebWork with SiteMesh is painfully simple: you don't have to do anything in fact. WebWork stores all its value stack information in the request attributes, meaning that if you wish to display data that is in the stack (or even the ActionContext) you can do so by using the normal tag libraries that come with WebWork. That's it!
One thing to note is when you want to pass a value from a decorated page to a decorator using the <ww:set> tag, you need to specify a scope (request, session, application) if the decorated page is invoked directly (not a result of an action). By default if no action has been executed and no scope was specified, the set value will only availlable from the same PageContext.