Online Database

I'm looking to provide a comprehensive online contact database that requires each user to register their details. Each user will fall into a predefined category. Some categories of user will be required to complete documentation online, which I will provide. The documents will be viewed as a web page and can be saved for completion at a later time or completed and sent to another user who can print them off at their end. There will be a requirement to display and confirm when the documents were completed and submitted to the another user. The site will be very simple but secure for users. The users account 'home page' will be displayed in the form of a wheel with the users picture or figure head or a logo in the middle representing the user who's account it is and the wheel will have numerous 'spokes' like a bike wheel and a box at the end of the spoke which will be another user attached this account. Click on the box and will take you to that particular users contact details. Each spoke (user) will be connect to the main user in the middle and the other spokes on the wheel!
It needs to be simple on the eye, simple to use and colourful. I am happy to use an open source database that can be customised. I am open to advice and assistance on how to make this project work.