The London Metropolitan Archives have been conserving, digitising and preparing for online publication the Great Parchment Book which is a survey of the estates of the Irish Society and City Livery companies in Northern Ireland. The survey dates from 1639, so this is an important online release for those of us who have family in Northern Ireland around that time period.
There is a 5 minute introduction video which I can recommend as it gives an overview of the history of the document. You can search under people, places and companies. there is also a blog where you can keep up to date on the project.
Sadly none of my Northern Ireland names come up, but it is worth the few minutes it takes to undertake a search to see if your family feature in this very interesting book.