Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
if you really want to, go to Activity Monitor (Apps -> Utilities -> Activity Monitor), select the process named Dock, and click the Quit Process button. Because it is part of the system, it will restart every time you log in/restart.

Why do you not want it?
 
Being that Dock.app is a fundamental system process, upon being killed it relaunches itself. To disable the Dock, it has to be renamed or moved out of the CoreServices folder and then stopped/killed.

This isn't really advisable, though, because cmd-tab, Exposé, minimizing, and Dashboard -- among any number of other things -- are unavailable. Your best bet is to place it in a corner, take out everything sans Trash and Finder, and then autohide it. In terms of usability/window management, the Dock truly is a critical system process. There's a thread related to this that you might be interested in here.
 
Most dock replacements complement the dock. Or if they're designed to completely replace the dock, it only hides it and doesn't exactly "get rid" of it. So the OP's solution would just be to hide the dock and get one of those 3rd party programs.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.