Bookmark : question of the day. Then the best thing is to get a book - I strongly recommend Khalid Mugal. Use the online mock exams for practise - but stick to a book. If you hit a dead end on a concept then google for some tutorial on that topic.
I would recommend KB's first. It is easier to understand and wrote to tackle the exam. Style and exam watch are very helpful for the exam. Khalid's are more in-depth which is one of the best book for SCJP. Books I have read to get certified are, KB, Exam cram2 (old but useful) and Khalid.
Mocks: John Hunt (easy and warm up questions) Marcus Green 1,2,3 (warm up type of questions) KB's Mock 1 and 2 (very close to the real one) Dan's (last few questions usually ruin my day) Java round up. (easy and warm up questions)
Unity can only be manifested by the Binary. Unity itself and the idea of Unity are already two.
K&B is the best book for beginners.Unless you have a few years of programming experience in java.khalid Mughal goes deep into the subject and sometimes confuses you.
One more thing i can say from my personal experience is that you have the momentum during the intial period and gradually it tends to slow down.Make sure you keep the momentum going until you take the exam.
All the best to you.
"Decide what you want, decide what you are willing to exchange for it. Establish your priorities and go to work."