See also the component section of our WIKI (might be more complete than the information here).
The sandbox is a MyFaces subproject that is a testing ground for potential new additions to the Tomahawk project. It primarily consists of components, but like the Tomahawk project, it can also contain validators and other useful JSF "goodies."
These components are a work in progress. In many cases they are checked in without being 100% feature complete. Testing is generally minimal and there is no guarantee that something you use in sandbox will ever be promoted to an official release in Tomahawk.