While none of the mailing lists really have a high volume, the lowest is the gpkcs11-announce mailing list. It is a moderated list and information about releases or general announcements will be sent there. For ongoing discussion about the usage of gpkcs11 you should subscribe to the gpkcs11-users mailing list.
If you are interested in participating in the development of gpkcs11, subscribe the gpkcs11-dev mailing list.