At the time of writing this blog post there have not been many documented stories of recovery from the Penguin algorithm change. Penguin initially rolled out on April 24, 2012 and there was a refresh on May 25, 2012 and there has not been another refresh since then.
I searched hard for stories of recovery from Penguin (i.e. after the May 25 refresh) and this was the only one that seemed plausible.
You can read the whole story of WPMU’s recovery on the SEOMoz blog.
The traffic drop for WPMU was dramatic and occurred coincidental with the initial rollout of Penguin. WPMU had thousands of client sites on the web, all containing backlinks in the footer text containing the anchor text of “WordPress MU”. Some could argue that this could be a brand name for the website, but in the eyes of Google, it was anchor text spam.
WPMU was able to remove a large number of these links prior to the May 25 Penguin refresh. After the refresh, they returned to their normal traffic levels!
You can read more, here about Penguin Update.