Umineko no Naku Koro ni is a series of visual/sound novels by 07th Expansion, part of their series "When They Cry", of which Higurashi no Naku Koro ni is also a a part.
I believe eight episodes are planned for Umineko (don't remember where I heard); currently, four have been released, and up through about the first third of episode four has been translated by the
Witch Hunt Translation Project; they also have links to sites that you can buy the game or download the demo from.
I've just finished playing/reading the first episode, and it kept me engrossed all the way through. If you can stand clicking through mountains of text, and you like mysteries, you'll love Umineko.