Seems that PRONI's 'Overlooked Archival Sources' lecture series has most definitely not been overlooked...
Lectures taking place this week and next (Using Church Records for Family and Local History - First Steps, with Valerie Adams (29 Jan) and Family trees - How GRONI can help them grow, with Alistair Butler (5 Feb), are fully booked, so you're out of luck if you hoped to attend.
There is limited space for the two following workshops:
Wednesday 12 February: "Maps from Snaps": Archive Mapping and Aerial Photography for Local and Family History, with Drew Ferris.
Wednesday 19 February: Understanding an Ancestor's Neighbourhood - The Griffith's Valuation Books, Maps, and Revision Books, with Dr Bill McAfee.
If you want to be at these free lectures, best book straightaway by email.