According to the Google AdSense blog, they are now allowing users to add up to 3 link units on their websites, compared to the only one link unit being allowed previously.   This is probably not significant to most Google AdSense users because generally the link units are not a very large source of income, but it can be if done properly. 

For more information about Google’s link units, or how to optimize their placement, I recommend you check out Dosh Dosh’s Ultimate Beginners Guide to AdSense Link Units Optimization.  Here Maki defines the ad unit, characterises it, and teaches you how to make money with it.  He even offers a quick tutorial on how to set them up on your site. 

In my opinion, this won’t significantly change your sites Google AdSense revenue, but it can definitely be helpful when the units are placed properly.  The reason they aren’t as useful as the ad units is because they require two clicks in order to earn money.  First, you need to get your readers to click on the link unit itself.  Once this is done, it will bring up a bunch of advertisements.  If those are also clicked, that is when you get paid. 

Its always fun to experiment with these things, so I have added another link unit just above my post meta section to see if that improves my CTR at all.   I am also considering a third one in the sidebar, but for now I’m just going with the two. 

Have you had any luck with the link units?