I'll never forget the day Panda hit for the first time, banned blogs, all top priority keywords out of index for months etc... The Penguin's influence was not that bad, as a matter of fact some keywords benefited from it.
If you were hit hard, my advice for you is to cut the black hat crap, and publish only quality content. Keyword stuffing and site cloaking will only do you harm. Substitute the badly affected keywords with some close varieties of theirs and you might want to lay low the link building process for some time.
Best of luck to you mate :)