We use a few methods for keeping track of project delivery and milestones.

They are all intended to be simple, accurate and accessible, in particular (with the exception of the Dropbox folder):

1. Documents, plans, approvals etc are all under version control and accessible by the internet with a web browser.
2. There is a project web site timeline which contains document changes, change requests, approvals/reviews and project milestones/events.
3. The project can be updated without access to the internet. Disconnected Operation is vital for our work at remote and secure sites.
4. The entire project can be exported to zip, git or as a tarball from the web interface or automagically every night.
5. The server is backed up atomically.
6. Users are all identified and changes are digitally signed so the web site provides a reliable record.
7. Changes to the project are added but the old history is kept forever (whence FOSSIL). This has benefits both for seeing whats happened along with ensuring that a compromised machine does not destroy the project data.
8. See How do we import project plans and milestones? if like most utilities you have a standardised project management tool.

Of course it is the people that really matter.

See also:

1. FOSSIL - Version Control and other project tools.
2. DBC - Design By Contract
3. Erlang - Concurrency and Reliabilty.
4. Pragmatic Programmer - one of the two books Phil I got a reference in.