Rick Riordan's first installment of The Kane Chronicles, The Red Pyramid is set to release in book stores tomorrow, Tuesday, May 4, 2010.
Here, you can read the first chapter of the book --
link
And here, you can hear from Rick Riordan himself what the plot of the new book will be --
link O68&feature=pyv&ad=5796588663&kw=kane%20chronicles
And his sequel series to the Percy Jackson & the Olympians titled The Heroes of Olympus, is set to have the first book, The Lost Hero, released on October 12, 2010. That's what I have heard.
Hope this helps!!!