Recent addition:

The Official Board

TheOfficialBoard.com is a source of company org charts and executive backgrounds. Free Membership lets you consult 15 org charts for free. Each time you add a relevant contact, you can view 10 additional org charts. Premium membership lets you consult all the org charts with no limits and contact executives by email.

Similar in some ways to LinkedIn, the crowd-sourced nature of this resource means that it is growing rapidly.