Google Apps recently made available dozens of Google services to Google Apps users. As part of this launch, Google AdWords is now available to our Google Apps users with their Apps accounts.
For those current AdWords users who've a Apps account, Google's currently in the process of wrapping up some necessary infrastructure work to ensure that the transition for those users will be a seamless process. For new users without data to transition, if your administrator has enabled this service you can begin using AdWords with your existing Apps account.
Google AdWords can be enabled by your domain administrator from the Google Apps Control Panel at https://www.google.com/a/[your_domain.com] (replace [your_domain.com] with your actual domain name).