Hi pinch, did you give Podio a try?
Basically, Podio is a project management tool that allows you to create your own app that suits your needs.
Once you are registered, here are some tips on how you can set up a app:
1) An isolated area for each client to view their project progress, see demos, etc
For project progress, there is a progress bar that you can incorporate into your app. If you prefer stages rather than % of completion, you can add the Category element to your app.
As for the demos, Links can be added to your app too if it is hosted online. Podio also integrates with Dropbox, Box and Google Drive so you can link your mockups to a project if they are stored using one of these services.
2) Graphics to show project stages, based on the agreed-upon workflow
You can add the Category element to your app to set this up. Add the project stages as options.
3) Indicators to show who is waiting on what information (i.e. waiting for the client to provide content)
For this, you can use the Category element again. You can probably label the options as "Pending Our Reply" and "Pending Client Reply".
4) Project timelines
You can use the Progress or Category element.
What I am explaining above might not make sense unless you register an account with Podio and start playing around with it.
By the way, I'm not paid to promote it. I'm using it for all my projects and I think it's awesome enough to be shared with fellow web workers.