SpryNetwork (USA company that I work with sometimes) have a range of sites providing internet services including broadcast streaming, hosting and web-design. They wanted a site which is common to all sites to provide a focus point for support and client administration. For this I developed the SpryAdmin site which uses a modular concept to load the correct sections of the site for which the user, or admin staff, has access too (for example, looking for SpryCast support and is loads only SpryCast modules).
SpryAdmin is an extensive and highly inter-linked site which can provide client, billing and ordering details quickly and easily. It allows orders to be completed and new package created. Basically any aspect of the SpryNetwork can be controlled from this one site. It also uses SpryPanel to add FAQs and documentation, and I developed a Trouble Ticket system to allow support admin and clients to have online conversation in non-real time.