How can I subscribe to the Bookshare discussion lists?

Bookshare Discussion forum
Bookshare has a general discussion forum open for any kind of discussion at
Bookshare Discussion List
This list is for Bookshare members to discuss Bookshare books, reading tools, tips, etc. 
Bookshare Volunteer Discussion List
This list is for Bookshare volunteers, specifically scanners and proofreaders, to discuss tips, books being worked on, best practices, and more.
These are very active lists, with dozens of messages each day. You can subscribe to these lists in digest form, which typically means one email a day containing all of the emails sent to the list that day.