International databases

Patient-Reported Outcome and Quality of Life Instruments Database (PROQOLID)
Patient-Reported Outcome Measures (PROMs, University of Oxford)
Patient-Reported Outcomes Measurement Information System (PROMIS)
ETS Test Link Database - more than 25,000 tests and other measurement devices
Database of questionnaires for measuring walking and bicycling (National Cancer Institute)
Short dietary Assessment Instruments (National Cancer Institute)
Health status and quality of life instruments (Medical Outcomes Trust)
Substance Use Screening & Assessment Instruments Database (University of Washington)
Finding Information About Psychological Tests (American Psychological Association)

Dutch websites

Database Meetinstrumenten in de Zorg 
Meetinstrumenten voor de palliatieve zorg
Vragenlijsten Fysiotherapie