I hate it when I am enjoying a series and then you have to wait for the next book to come out (it's better than the series ending though).
I am waiting for a few books to come out:
From Dead to Worse - Sookie Sackhouse Book 8 - May 6th (Can't wait!)
Blood Noir - Anita Blake Book 16 - May 27th
All Soul's Night - Blood Ties Book 4 - June 1st
When Twilight Comes - The Gardella Vampire Chronicals Book 4
Bitten To Death - Jaz Parks Book 4 - August 12th
Breaking Dawn - Twilight Saga Book 4 - August 2nd (I may not read this and just have someone tell me what happens).
There is probably more, but this is what I can think about so far.