Expat Centre Leiden: a great starting point for all kinds of aspects of living in the Netherlands:  https://www.expatcentreleiden.nl/en

Home in Leiden: another website with all kinds of relevant information and links for life here: https://www.homeinleiden.nl/

Leiden Expats: A Facebook group where all kinds of topics, questions and events are shared:  https://www.facebook.com/groups/leidenexpats

Leiden Community: Also a Facebook group – for internationals wanting to meet up with others: https://www.facebook.com/groups/612846103265401