The main JBoss site is www.jboss.org. The site hosts forums, e-mail lists, download pages and documentation. The JBoss documentation is a bit spotty in places, doesn't always explain things fully and assumes a fair amount of knowledge regarding EJBs. However, it does describe most of what you need in fairly plain language and gives you some good working example code that you can use.
O'Reilly's book Enterprise JavaBeans, written by Richard Monson-Haefel, is an excellent introduction to the subject of EJB. Combined with the tutorial and introduction at www.jboss.org, this book should make it possible to get started with some simple EJBs in a relatively short period of time.
Ant, Java's answer to make and Makefiles, is part of the Apache Software Foundation's Jakarta Project. You can download Ant from jakarta.apache.org/ant.
Sun's site, java.sun.com, has a great deal of information about the J2EE specification, Enterprise JavaBeans and general use of server-side Java.