Check these really good sites to test yourself or be familiar with the test format before go for the real exam.
1) http://www.jchq.net/ ( There will generate randomly one question per day for you to answer with full explanation full the answer )
2) http://www.examulator.com/phezam/login.php ( Contain 60 question to answer and is a simulator for the real exam ) Recommended !
3) http://www.jdiscuss.com/ ( Another site generate 1 question per day for you to answer with full explanation ever better compare to jchq.net . There also include a free mock exam )
Ref : lcmbryan’s blog
Orange Slate 
MUST mention about ExamLab
http://www.examlab.tk
They have free mocks for both 1.5/1.6 versions. Really helped me.
Thanks for the links
http://www.geocities.com/sunjava4u/index.html
Even this website has loads of links.
Thanx Kishna 🙂
I have few questions on scjp 5.0 :
http://www.javabeat.net/javabeat/scjp5/mocks/index.php