How do you organize, maintain edits, revisions and the relationship between:

1. Proposals
2. Contracts
3. Change Orders
4. Deliverables
5. Projects

How do you organize your projects for re-usability?

For example, is there a way to add tags to projects, to make them more accessible?

What's a good data structure to dump all my files on an internet server for easy access?

Presently, my work folder is setup as follows:

(1)/work/
 (2)/projects
  (3)/project_a
   (4)/final (which includes all final documents)
    (5)/contracts
    (5)/rfp_rfq
    (5)/change_orders
    (5)/communications (logs all emails, faxes, and meeting notes and minutes)
    (5)/financial
     (6)/paid
     (6)/unpaid
    (5)/reports
   (4)/old (include all documents that didn't make it into the project_a/final/ 
  (3)/project_b
   (4) ... same as above ...
 (2)/references
  (3)/technical_references
  (3)/gov_regulations
  (3)/data_sources
  (3)/books
  (3)/topic_based (each area of my expertise has a folder with references in them)
 (2)/business_contacts
  (3)/contacts.xls (file contains all my contacts)
 (2)/banking
  (3)/banking.xls (contains a list of all paid and unpaid invoices as well as some cool stats)
  (3)/quicken (to do my taxes and yada yada)
   (4)/year
 (2)/education (courses I've taken
  (3)/webinars
  (3)/seminars
  (3)/online_courses
 (2)/publications (includes the publications I've made
  (3)/publication_id

We're mostly 5 people working together part-time on this thing. Since this is a very structured approach, I find it really difficult to remember what I've done on previous projects and go back and forth easily.

What are your suggestions on improving my processes? I'm open to closed and open source software (as long as the price isn't too high).
I also want to implement a system where I can save most of the projects online to increase collaboration and efficiency and reduce bandwidth especially on document editing.

Imagine emailing a document back and forth 5-10 times a day.