The links below are a few that have been found to be useful by Designated Pilot Examiners.
*If you find others that you think should be shared with the community for quick access, regular use, or that are otherwise difficult to find when needed, please share them with us and we will add them to the list.
Designee Management System - System DPEs use to notify and track practical test activity.

Designee Currency (Online) Training Registration - This link will take you to where you can sign up for the online training that designees take every two years as a part of the currency process.

8000.95 - Designee Management Policy - Including Change 1 thru 5

AFS-640 - Designee Standardization Branch at FAA.

FSIMS - Flight Standards Information System - This site includes the 8900.1 guidance and access to all current FAA guidance documents.

FAA Airman Testing (PTS and ACS Standards) - Current FAA Airman Certification Standards and Practical Test Standards can be found here. Current pdf versions of these documents can also be found in the shared documents of this website for download (these are also iPad friendly).

AC61.65H - Advisory Circular that includes endorsement requirements and testing guidance for practical tests.

FAA Handbooks and Manuals - Current FAA Handbooks and Manuals can be found here. Current pdf versions of these documents can also be found in the shared documents of this website for download (these are also iPad friendly)

Aircraft Registry (FAA) -  This link is to the FAA online aircraft registry. If an examiner has a question about the airworthiness or registration of an aircraft this is a good place to do a first check.

FAA Aviation Regulations 14 CFR - Current FAA Aviation Regulations.