Not sure if this works for everyone, but it worked for me somehow. I don't know if my domain got penalized during penguin, but I know I lost all rankings. And I was within top 5 for some really strong keywords. What you can do to get your rankings partially back, is a pernament 301 redirect. BUT, not from the penalized domain to a new domain! First do a redirect from the penalized domain to a random domain(not brand new) and from that domain to the new domain. You can simply move all the content from the penalized domain onto the new domain. The penalty will be transfered to the middle domain, but not on the 3rd domain. You won't get all rankings back, I am not even close to top 5 anymore, but at least I'm back within top100 again and can start working on the seo again. I have high competition keywords which I would de-rank for quick even with no penalty, if I didn't work on them, so this ranking loss is not really a surprise(after so many months of doing nothing there). And with the 2 domain redirect you lose some domain and link power, too, BUT its always better than to let the domain die.