our 'penguin' sites recovered a few % around the 19th May
For our site that was hit by Penguin, it was May 21st that we saw kind of recovery. Taking seasonality into account (using year over year data) we gained back about 40-50% of what we lost on April 24th.
Very few changes to our site... but we did chase down poor quality backlinks and request removal. That is something we would have simply ignored in the past.
We have not seen any recovery of the main terms we used to rank for pre-penguin.