Definitly worth taking atleast once. 44 TipSmart's sample paper 24 Questions mostly based on Java language basics which is important for SCJP 2 exam. Parikosh's exam 17 Thought provoking questions. Please do send your comments to Parikosh for his helpful work. Has Quiz and Mock type exams.
Author plans to add few more mock exams.
Please check out this link often to see if there is any new mock exam. 47 Sahir's Mock exam 100 Has 10 questions under each SCJP objective. It is an applet. Author plans to give out the application version soon. One click on the entry and you go to just the right spot that discusses material that covers the objective the question was covering.