Client Management (for Web Designers)

I've noticed that some design studios or web design companies offer private client areas, whre the clients can login and do some things. Having never actually been into any of these areas, I've always wondered what kind of information or what kind of special resources you would offer your clients in such a client area where they would have to login?

I'm considering having some kind of web-based client management system to better service my clients and be able to keep all of my web design related communications in one place instead of scattered in my email inbox among other things like personal emails.

Additionally, your client may actually be a group of people more likely than not, say for example if you're doing a job for a company where the President, VP or director of sales all want a say in the design process. Having a client management system would be a better way to centralize communications for everyone involved.

My question, for web designers, is what kinds of features would you make available to your clients in this client management system to most effectively service them. Some things that immediately come to mind is:

- Some kind of messaging system, that would work just like emails, just all consolidated in the system

- A progress bar that I can update manually to show them at what percent I believe their project is complete, with an ETA of their web site.

- Scheduled Billing system, set up to properly charge the client on their quoted invoice. (Like for example, charge 50% of the total invoice when 50% complete, then require the client to pay the rest, then make their files available in the client area once paid)

Anything else? These are just the basic things I deal with for any client via emails.