Roberto, if you think some of those discussions are particularly helpful for someone about to start out with the exam, please feel free to add links to those to the FAQ. After all, you took the exam, and should know what did or did not help :-)
I considered SCJD assignment as a distributed, multi-threaded application developed using RMI or Sockets for server and Swing for client. The key topics to understand for SCJD:
* RMI or Sockets
* Java file I/O and synchronization
* locking (some OS book should shed some light)
* OO design and 2-/3-tier architecture
If you haven't got the assignment, read about and code some file I/O, RMI and Sockets. Then threading and locking. And finally swing.
If you got the assignment do the same thing but using the assignment's code.