When you want to create a DVD with iDVD, and have edited in Final Cut Pro, it seems impossible to get the markers over to iDVD as chapter marks. The unobvious thing to do is this: you have to edit the markers in Final Cut to make them into chapter markers. Then when exporting the movie to Quicktime, choose to export the chapter marks, too, and save the movie as not self-contained (this just saves disk space).
When you drag or import this movie file into iDVD (and iDVD Preferences are set to "create chapter menus"), you get the chapter submenues created. I tried for ages with normal markers and it drove me nuts to export the movie, then have to open it in iMovie just to add the markers.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20041229155439470