We have created a listserv specifically designed to assist people with EndNote (and other citation management software) needs.
Simply e-mail firstname.lastname@example.org, and one of the specialists will reply to your email.
Click on Organize and Manage My Groups.
Select which groups you would like to share.
Add the e-mail address of the person you want to have access to it and decide if that person should have read only or read/write access to your citations.