If you're referring to the M8 and M9 digital pictures, they share a sensor type and manufacturer: The Kodak KAF series CCD sensor.
There is something a bit different about the colors and film-like qualities of these sensors. It's my belief that Leica chose these sensors (and still uses them) because they match the Leica film pictures look so well.
Much of those same qualities are shared by the Olympus 4/3 cameras that used this same series of sensor: the E-1, E300, and E500. (I might be leaving one or two Olys out here - but unfortunately neither the E-3 nor E-5 used these sensors.)
These aren't great at low light due to noise, but they do have great dynamic range given enough light. Pick up an E-1, you'll love using it during the day. The pictures from it are pretty darned special too. The E500 has more megapixels (closer to that of the M8), but it's a bit more of a challenge to get "the look," at least for me.
The lens will have some part of the puzzle as well. But from the photos I've seen, it seems to be a bit less about the lens (as long as it's a great lens), and a bit more about the sensor.
Here are a few photos from the E-1:
and one from an E500: