In my opinion, the project management templates should be developed by your PMO and not downloaded from a website.
In any case, just search Google for "project management templates" and you will see a vast selection of free and paid project management templates, many of them are Excel based (so you need to have Excel installed).
The most important project management templates to look for are:
- The project charter template (or project proposal template)
- The schedule management template
- The cost management template
- The risk management template (including the risk analysis template)
- The communication plan template
- The issue management template
- The contract/vendor management template
- The change order request form
- The lessons learned template
- The acceptance template
Make sure that you modify all the templates to fit your needs, and ensure that these templates are generic for your business (so you won't have to change the template for every project, which defies the whole point).