If you go to http://www.google.com/webmasters/ and log in, I think there’s a link somewhere on one of the pages to “Request a review”. I don’t know exactly where to look for the link.

The following document contains an image of the new Webmaster Tools Interface, as it relates to sites with malware.

Google Webmaster Tools
Google Malware FAQ – Request a Review

It’s my understanding that you must click on the site’s URL to view the Dashboard for that site. Once you see the Dashboard, there should be a red bar with a malware warning and a [ More details ] link. Click on [ More details ] to display the screen that has the [ Request a review ] link.