Danny Sullivan at Search Engine Land put up a great Penguin article with some new quotes from Matt Cutts. We've referenced some of the points made in other articles, but one important thing to note from the whole thing is that Cutts pointed to two very specific videos that people should watch if they want to clean up their sites and recover from the Penguin update.
We often share Google's Webmaster Help videos, which feature Cutts giving advice based on user-submitted questions (or sometimes his own questions). I'm sure we've run these in the past, but according to Sullivan, Cutts pointed to these:
Guess what: in both videos, he talks about Google's quality guidelines. That is your recovery manual, as far as Google is concerned. Here are some articles we've posted recently specifically on different aspects of the guidelines:
So, in your recovery plan, take all of this into account, and these tips that Cutts lent his seal of approval to.
And when all else fails, according to Cutts, you might want to just start over with a new site.