Google had announced early this summer that they were launching, via invite, a way to automatically import Salesforce data into AdWords. Now, it looks like this function is finally rolling out generally.
Salesforce.com is an option available under the Linked accounts menu.
After getting everything set up, the linking allows the Google Click ID (GCLID) to pass to Salesforce whenever a user completes a conversion action, such as filling out a lead or downloading a whitepaper after clicking on an ad. Marketers will select a milestone event in Salesforce that they want to pass back into AdWords. Once this happens, AdWords will automatically check Salesforce on a regular basis to import those milestones and log them as corresponding conversion events at the keyword level.
More details are available on the AdWords support page.