What do you need to achieve your projects?
Have you already done some servlet and EJB programming? If so, I suggest you start with the Getting Started Guide: http://docs.jboss.org/jbossas/getting_started/v5/html/.
Another good getting started reference is the book JBoss at Work: http://www.amazon.com/JBoss-at-Work-Practical-Guide/dp/0596007345, though it does not cover EJB3.
If you have not done any servlet programming, look at Core Servlets and JSPs at http://www.coreservlets.com/. The price is right (free!) but the version of servlets/JSPs is rather dated.
If you have not done any EJB programming, I recommend just starting off with SEAM. See http://labs.jboss.com/portal/jbossseam/?prjlist=false
And of course, you will want to read the JBoss docs at http://labs.jboss.com/portal/jbossas/docs