I'd suggest taking a look at David's book, especially pages 161-162, and pages 166-167.
161-162: Here, you'll see some information on setting up group discussion databases. Although Lotus Notes makes this very easy, it's possible to do in a "folder" within any open drive on your computer. Simply title the folder with the project name and populate it with any documents related to that project.
166-167: When filed, these documents (Word, Excel, etc) become non-actionable reference or project support. As such, they must be reviewed as often as necessary to ensure that all the next actions are defined.
Where and how you keep these items will depend on your own personal system. Currently, within My Documents, I have sub-folders for such items as:
>>David Allen Company
Then, for example, within the David Allen Company folder, I have another sub-folder titled >>Getting Things Done Seminars. My Word, Excel, and picture documents are stored there. Again, I can access them easily, and, for now, they are out of the way while I'm working with the desktop computer.
Hope that helps!