metadirectory

keeping OpenLDAP and Active Directory in sync (windows server 08R2)

I've got a Windows Server box running AD, and a CentOS box running OpenLDAP in a mixed windows Linux network and I want to keep the two in sync. Preferably using free software/just some configuration changes. anyone know how to make these 2 authentication systems play nice? any syncing would have to be done over SSL for security reasons....