Yes, TesTeq is right. I've just taken a blank Word document, populated all my own headings but not filled in all the detail, and called it "Plan Template", and saved it in my electronic reference folder with all my other templates (also made by me). It just saves time rewriting and formatting all the headings, and I like all the project plans to look roughly the same. It's based on GTD's natural planning model but of course with other info relevant to my job. I have one Word file per area of focus.

Some typical headings I use:
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