Power and Majesty [Creature Court Book One] by Tansy Rayner Roberts will be released from Harper Voyager in June 2010. I have it on good authority that it may be in bookshops in Australia & New Zealand as early as the 25th May!
Cabaret of Monsters [Creature Court Book Two, working title] is due for release in December 2010 and Saturnalia [Creature Court Book Three, working title] in July 2011.