This week's book giveaway is in the OCAJP forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide 1Z0-808 and have Jeanne Boyarsky & Scott Selikoff on-line! See this thread for details.
My gut feeling is that Jini is being investigated a lot, but not seriously implemented by many major enterprises. If you know of any real-world Jini usage, please let us all know. Jini is related to EJB in that they are both based on Java, and in particular RMI and serialization, but not any closer than that. EJBs can be used to provide a "wrapper" round Jini services to make them available to a J2EE system, but then so can any other Java class.