This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
I realize that you are specifically asking about websites. Have you considered additional books that provide training for the exam, as far as finding exercises?
Anyway, one possible website for exercises is the site for Bruce Eckel's book, "Thinking in Java". Be aware, though, that the book is almost 1500 pages long and (probably) goes far beyond what you need to focus on for the exam.