Nope, the 360 does not, and Microsoft have said will never, come with a HD drive.
As vehelpfulguy says they do plan on releasing an external HD drive. Games will still come on DVD so the HDDVD drive will just be for movie playback.
Allegedly.
the xbox 360 contains an HD drive ie a Hard Disk drive but later this year they are also releasing a HD dvd drive ie High-Definition drive to play hi-def dvd's or hd-dvd's.