Here’s a great YouTube Video from Google’s Matt Cutts on how long it takes a Google Reconsideration Request to process.
What is a Reconsideration Request?
Sometimes referred to as a reinclusion request, Google has a formalized process by which it considers removing manual actions taken against sites in violation of its guidelines. It is essentially an apology letter to Google. You admit you messed up, tell them how you fixed it and promise you won’t do it again. If they think you’re sincere and that you have fixed the problems and aren’t going to do it again, then they lift the penalty.
After the website owner conducts checks to determine that Google has blacklisted the website (search for your domain in Google, and click the link to visit your site), the only recourse available is to fill out a “reconsideration request” via an online form.
Tips on submitting a Google reconsideration request.