Point-&-shoots typically use CCD. More expensive ones and SLRs typically use CMOS. The last (only?) Canon SLR to use CCD was the 1D.
CMOS has two advantages: faster data transfer and less heat. CCD can be considered the superior technology because all of the highest quality imaging equipment use them (e.g. astronomical equipment), but for whatever reason, CMOS has lended itself much better for consumer use.
MFDBs and Leica use CCDs because they all get their sensor from Kodak. Whether Kodak made a specific decision to only make CCD, or if they only do so because they're incapable of making a quality CMOS sensor, I don't know. In any case, Kodak's sensor design/tech/fab is way behind Sony/Nikon/Canon, so whatever theoretical advantages CCD and MF sensors have are largely lost. For example, MF sensors would theoretically have much better high ISO performance than APS-C sensors...but they don't, and it's not even close.