There are a few larger sensor but smaller size cameras but they don't quite fit comfortable into a normal pocket (you have to have a big pocket):
Panasonic GF 1
Sigma DP 2 (this one has no zoom)
The Olympus EP-2 and Panasonic GF 1 and micro 4/3 systems, can change lenses with a good amount of zoom but that lens is bulky and will definitely not fit into a pocket. These 2 cameras have good quality images, on par with the entry level D-SLRs.
If you give up the large sensor, then there is the Canon G11 and S90. Sony is pushing out HX5 with 10x zoom but prior reviews of the back illuminated CMOS sensor is not quite the answer for PS camera in low light performance.
So your dream camera does not exist yet. If you want a smaller sized camera with D-SLR quality, the closest you can get is the Panasonic GF 1 and Olympus EP 2. But they can't fit in your pockets yet, and you need to change lenses like a D-SLR.
What camera fits these criteria?
(1) fits in my pocket
(2) big sensor
(3) no shutter lag
(4) lots of zoom
Based on my preliminary research it seems that (3) and (4) are more or less incompatible, and when you throw (2) in there it becomes downright impossible to find something. Basically I want something I can take around the city and whip out any time to take high quality photos. Who doesn't - I know. But any ideas? Price not really a consideration for now.