Well I just took the exam, and passed with 91%, so I'm off to celebrate this afternoon!
As for preparation:
Well of course this forum... I also bought both the Head First Servlets and JSPs book and Charles Lyons SCWCD Study guide, read both and read bits and pieces from the Oreilly JSP book. I found all of the above to be very useful. I printed off Frederic Esnault's notes - which I found great, and made a few (not many) of my own on cards.
I tried out some stuff I didn't understand on Suns AppServer software to help cement the ideas.
As for mocks, I did the demo mocks from Whizzlabs, Certgear and Enthuware which highlighted a few issues, as well as the HFSJ mock. If you want to see more representative questions, Sun themselves will give you access to 10 sample questions if you sign up for them.
How long did I prepare for? I bought a voucher for the exam in one of Suns offers nearly a year ago along with SCJD part 2, and have been vaguely trying to learn the material since. I only started studying hard though about a month or so ago because the voucher was going to expire!
Now - off to celebrate and thanks to everyone for a great forum - the stuff here has been invaluable!