PreCentral reader cdowers managed to get the webOS running on a Dell C600 laptop, and it took him little to no effort at all. He just took the webOS image from the emulator, stuffed it on an IDE hard disk, and it booted successfully without any modifications.
There are problems, of course. Currently, navigation is done through the keyboard alone, so mouse support would really be a welcome addition. At this point, it can only run at phone resolutions, but it shouldn't be too hard to support PC resolutions, since "many of the apps seem to be okay at higher resolutions" (the webOS has always been designed with multiple resolutions in mind).
There are more issues to overcome than just these, of course, not least of which the fact that distributing such an image would probably not be legal. Luckily, though, Palm is very supportive of the geek community, and they haven't undertaken anything against similar modifications in the past.
If you want to help out, follow this thread and offer your services.