Theresa Neil, author of Designing Web Interfaces, has identified 12 standard screen patterns, these being (in no particular order):
- Master/Detail
- Column browse
- List item
- Search / results
- Filter dataset
- Form
- Pallet / Canvas
- Dashboard
- Spreadsheet
- Wizard
- Question & Answer
- Parallel panels
- Interactive model
- Blank state
Source: http://designingwebinterfaces.com/designing-web-interfaces-12-screen-patterns
EDIT: Three more were added in 2010:
Source: http://designingwebinterfaces.com/ria-screen-layouts
You could try determining a unique vocabulary, leveraging what this site has to offer. You can then apply this set of terminology across your templates. You'll soon start seeing what is entirely unique, and where there are very close similarities.
Do not trust the vocabulary blindly though, as it may limit how you express something, meaning there may be differences not expressed.