I use Word and Pocket Informant on the iPhone, I don't bother syncing because I always have my iPhone, so use it in isolation to the computer.
I started using Excel, but found it too limiting to hold all the project support and natural planning info, and Word does this as well.
I have one Word file per Area of Focus, and it contains all the support info and project info. It does become quite a long document, so I use the Document Map pane to navigate around it.
Some typical headings:
LEADERSHIP
-Context
-Drivers for change (incl corporate strategic framework and legal info)
-Purpose
PEOPLE
- internal stakeholders
-external stakeholders
-agendas and meeting notes
INFORMATION, DATA & ANALYSIS
- Information (glossary, general info)
-Data sources
-Past work
OPPORTUNITIES
- Ideas
COMMUNICATIONS
- Reports
PROJECT 1
- Purpose
-Principles
- Outcomes
-Brainstorming
-Organisation
-Actions & Checklists
I did start with a Word file for each project, but found that a lot of support info was common amongst many projects and so created a common file.
I also always put a * in front of any heading where there is outstanding actions, or needs to be reviewed in the weekly review, so by looking at the document map I can see all the sections which need review very quickly.
I then manually put next actions only into Pocket Informant, all future actions stay in the Word document.