This site is about iMovie, the video editor, so why an iDVD-related topic? hmm, well, easy: most people 'mix' both apps, and Apple 'bundles' them as iLife.. finally: we waant our iMovies on disks, don't we.. ? ;)

 I actually count basicly FOUR methods to create a videoDVD WITHOUT a menu at its beginning... : 

Very easy:

In iDVD you'll find a lil' switch aside the Play button... 

click on that, and you see ... ehm, the structure of your project. The first box is the 'Autostart' box... drag form your media-bin into that box ... (1)

In effect, when your disk is finished with playing your movie, it will jump into a menu ... so, one option is, to set the Autostart-movie to 'loop' (2), or 'kiosk mode' ... but then, your disk will never finish playing.. 

So, probably, a simple 'customied' menu, with a black background and a text-box telling 'The End' is maybe another option ... 

Very  Easy, too

• Export your project back to tape
• Import your tape into a new 'One Step' iDVD project ... 

iDVD will then create 'just a plain disk' of your tape (=movie). 

Easy

3rd party Burning App Roxio's Toast allows the creation of no-menu-DVDs ... 

Toast 8

 Toast 6

Just drag your iM's project files (for vers.≤6 of iM) into the Toast Window and check the box 'Autoplay'

Mish' Hard Way

AD's forum member Mish Mumkin published this method, which is no beginner's task, ...
You need a free tool,  myDVDedit, you get it here:  http://www.mydvdedit.com 

follow these steps:

• create a disc image of your iDVD project, then double-click to mount it.
• Extract the VIDEO_TS and AUDIO_TS folders to a location of your choice. select the VIDEO_TS folder and hit Cmd + I to open the Inspector window
• Set permissions to "read & write" and include all enclosed items; Ignore the warning.
• Open the VIDEO_TS folder with myDVDedit. You'll find all items enclosed in your DVD in the left hand panel. 
• Select the menu (usually named VTS Menu) and delete it 

• Choose from the menu File > Test with DVD Player to see if your DVD behaves as planned.If it works save and close myDVDedit.
• Before burning the folders to Video DVD, set permissions back to "read only", then create a disc image burnable with Disc Utility from a VIDEO_TS folder using Laine D. Lee's DVD Imager:
  http://lonestar.utsa.edu/llee/applescript/dvdimager.html

...

Have Fun With iMovie!