The only sample project is Denny's DVD and the real assignments will not be shared, because that's not allowed.
In my opinion
you should first have a couple of years of experience as a professional programmer/developer, before taking the SCJD. Because someone with no (or limited) experience can not be a (good) (certified) developer. You just need real life experiences. It is just a process: you start as a programmer, when working as a programmer you become more experienced and you learn a whole lot which will make you a better programmer/developer. And then it's time to take this certification. I downloaded my assignment when I had 3 years of experience being a
java programmer/developer (and finished the assignment due to lack of time 2 years later).
When I was a recruiter and I saw a CV which mentions SCJP and SCJD on it, but without any real life experience, I certainly won't hire that person, because best learning school is working for a company (with other more experienced developers which share their knowledge,...). But as I said: that's just my opinion about taking SCJD.
Other questions like yours were answered
here and
here.
And if you want a pinpoint approach for scjd, you can have a read of the stories of ranchers passing the SCJD exam (you'll find a link to mine in my signature).
Kind regards,
Roel