I presented a Spring / EJB 3 Comparison/Integration talk at the IndicThreads Java conference in Poona. It was very well received. Here is the link to the presentation for your reading pleasure.
It is primarily based on the contents on our book EJB 3 In Action and my research with my coauthor Reza Rehman on this topic.
All EJB 3 books in the market ignore existence Spring considering it as a competitor. Even the classic Java Persistence on Hibernate says nothing about Spring framework. However EJB 3 In Action takes a pragmatic approach and tries to recommend whenever Spring makes sense. Although Spring and EJB 3 are viewed as competitors it can be used complementary technologies and a whole chapter of EJB 3 In Action is dedicated to this integration story. So why wait .. buy a copy for yourself :)