First 20,000 only.

Link

The site is in French, but it's fairly straightforward.
Translated Version for reference

1. You just need to fill out the first couple fields and last three:

Nom (Name)
Prénom (Last name)

You can skip the middle section labeled "Communauté".

Fill out the following:

Adresse email (Email Address)
Vérification email (Repeat Email Address)
Date de naissance (Date of Birth)

2. Click the confirmation button.

3. Check your email and click the link inside to confirm your email address. You have to do this in order to be registered.

4. Profit.

The confirmation page roughly translates to "Welcome to the enrollment program to play the beta test for Call of Duty: World at War, in multiplayer mode on Xbox Live.

You are registered to receive a key to the beta of Call of Duty World At War on Xbox Live."

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

After you register, you should get an email within 30 minutes:

Bonjour,

Vous désirez participer à la Beta Call Of Duty World At War.
Vous avez 48h pour valider votre email en allant à l'adresse
ci-dessous ou en recopiant le lien dans votre navigateur.

http://www.gamekult.com/tout/betacod5.html?action=2&email=INSERTYOUREMAILHERE&codeverif=206

Vous serez alors inscrit pour recevoir une clé pour la bêta.

Translation:

Hello,

You want to participate in the Beta Call Of Duty World At War.
You have 48 hours to validate your email by going to the address
below or by copying the link in your browser.

http://www.gamekult.com/tout/betacod5.html?action=2&email=INSERTYOUREMAILHERE&codeverif=206

You will be registered to receive a key for the beta test.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Hope that helps!

Wikipedia

Credit: Revin9k

Is this good for NA, or is this beta only open to EU?

Green as usual iceui2!

I did

Getting slammed!

Just got the confirmation, I assume we wait for the key now....

thanks, got 10 emails registered so far. Think there is going to be an eBay market for these?

i got the registration confirmation email in my yahoo email. finally! took forever. yahoo mail is so so slow. anyway, clicked on link (site getting hammered, but worked) and now waiting for key to arrive. thanks op.

sit's getting hammered or something

Please change the title. This isn't Call of Duty 5 - it's Call of Duty: World at War.

Yes, it's the 5th installment, but is not considered "Call of Duty 5."