To quote Chris_R from this thread [webmasterworld.com], which may be helpful to you:
put "reinclusion request" into the title of the email and send it to support@google.com
coconutz
9:55 am on Apr 28, 2003 (gmt 0)
"If you think your site may have penalties for violating our guidelines at one time, but the site has now corrected any problems, you can send an email to webmaster@google.com with the subject line "reinclusion request". Wait to email us until you're sure your site complies with our quality guidelines at [google.com...]"