Several books on JDK 1.5 (Java 5) but none on the 1.5 Certification exam.
Two I can recommend are the one by Peter Van Der Linden (its gotta be good as it mentions me) and the 2nd Edition of Head First Java. (I don't actually have a copy but I keep reading it in Borders
)...
Sierra and Bates are furiously working on a new version of their Certification book for the 1.5 exam, and I am working on material myself.