Sony's Cambridge Studio is one that was acquired very early on in the PlayStation business, and they've been with Sony since 1997. They've worked on numerous games such as MediEvil, LittleBigPlanet (PSP) and much more.
The Cambridge Studio has also contributed to Killzone 2, Heavenly Sword, Wipeout, PlayTV and EyeToy.
Sony recently updated their website showing a vacancy for a lead PS3 engineer. The job vacancy states:
"We are looking for an experienced lead programmer to head the engineering team for our next PS3 game title as it enters the production phase..."
This means that they are definitely developing a game, and not an application such as PlayTV or PlayStation Home.
"...The position offers an excellent opportunity to play a key role in the shaping and delivery of an exciting new IP for the studio, and would suit a senior engineer wishing to pursue a managerial track to their career path."
The Cambridge Studio hasn't fully developed a PlayStation 3 game since the console released, and have only worked on PlayTV and PSP. Their experience with Eyetoy suggests that this new IP will be a motion control game. Whatever it is, let's hope it is good.