The Google AdSense blog rolled out an enhanced reports for their Link Units, that lets you view the performance of link units separately from other AdSense for content units. The new improvised, link unit-specific reports contain more information about link units.
To view your new, improved reports, visit the Advanced Reports page under your Reports tab and select AdSense for content. You'll notice a new option to customize your reports -- 'Choose Units'. A 'Combined' report will look just like the data you're used to seeing in your AdSense for content reports, while choosing 'Ad Units' or 'Link Units' will help you look at things with more granularity.
Google, AdSense, Earning, Performance, Reports