Membership driven websites are a joy to work on as there are so many wonderful areas of design collaboration. Each organization is as unique as their needs, and membership. Most should have a "Members Only" section where content and information may be imparted to them only. This helps build a sense of community and in fact, many have a built-in Facebook type of Community section which allows for groups, posts with pictures, video sharing, and more.
Each will require a Blog and or Latest News section(s), some will require multiple layers of access control, others may need to be displaying information both publicly and privately, all are designed to interact with larger audiences.
I have spent 26 years building and maintaining large membership driven websites for organizations. For over a decade these included The American Financial Services Association (AFSA), The National Foundation for Credit Counseling (NFCC), The Consumer Data Industry Association (CDIA), World Finance, and dozens more.
Agilium Worldwide has 28 members in 29 countries. Together we have created a website that enhances each members' online presence and SEO, attracts new membership, and informs current members with their Latest News. Each member's page has high resolution copyright-cleared photography specific to their geographical location. I invite you to explore several member's pages. The website is designed to promote each member with multiple internal and external links. Their entire website is instantly translated into a foreign language at the click of a flag.