Google Adsense Integration 
As of vBulletin 3.8, we have partnered with Google AdSense to make it easy for you to sign up with AdSense and make money with your online community! More information is available about Google AdSense on their website

To get started, you must create an AdSense account or associate an existing account via the vBulletin Members' Area. Once your account is associated with us, Google AdSense will automatically be available to your forum the next time you download vBulletin.
Warning:
If you have not associated or created an AdSense account with us, the below options will not be shown in your administrator's control panel!
After you have downloaded vBulletin with Google AdSense integrated, you should follow the standard upgrade instructions. After logging into your administrator's control panel, you will see an Advertising block in the left-hand navigation panel.

Now you must choose the type of integration you want:

The available Google AdSense packages are defined as:

Low
  1. A small 5-link advertising unit under the navigation bar. This location only shows text ads in the Low package.
  2. A small advertising unit at the footer of the page.

High
  1. A medium advertising unit under the navigation bar.
  2. A nearly-square advertising unit within the first post of a thread. This only shows for guests.
  3. A medium advertising unit at the footer of the page.

Note:
It has been reported that some ad blockers can interfere with setting up Adsense via these instructions. If you have a problem try temporarily disabling your ad blockers.
Trevor Hannant 04th May 2010, 07:48am
If you've already setup your AdSense link through the Members Area, simply FTP the following four files in ASCII mode to your server from the new download:

/admincp/deployads.php
/includes/adsense_templates.php
/includes/init.php
/includes/xml/cpnav_ads.xml

If you do not see the Advertising block in the left-hand navigation panel after doing everything correctly, hard refresh your ACP page (or log out of the ACP and then log back into the ACP).
Mike Cebulak 16th Jan 2013, 10:26am
Note: You also may need to make sure you have this permission set for your Admin account:

Admin CP -> Usergroups -> Administrator Permissions -> Can Administer Ads -> Yes