I recently completed a project for a client to re-design the landing page they use for their Google Adwords Pay Per Click campaign.
The results of the test just came in and with a few clever design modifications I doubled the effectiveness of their original landing page (conversion rate rose from 5% to 10%, and cost per converted lead was reduced from $34 to $17).
That means for the same media expenditure they are now driving twice as many leads! (Actually, it's better than that because the optimized page is increasing the number of leads from their organic search traffic and their website browsing traffic, too.)
This presentation shows you step-by-step the methods used to optimize the landing page.