Just found online today the title for the new spin-off "Camp Half Blood" series by Rick Riordan!
Due out Oct. 12, 2010 is The Lost Hero.
The Heroes of Olympus: Book one
Description from Amazon: It was hard to say good-bye to Percy--but fans don't have to! A lovable new generation of demigods have their own prophecy to prepare for, and their hero Perseus Jackson just may turn up in times of need.
*squee* Cannot wait for this one!!!