Biodiversity
National Biodiversity Data Centre - http://www.biodiversityireland.ie/
Biodiversity Maps - http://maps.biodiversityireland.ie/#
Heritage
National Monuments Service - http://www.archaeology.ie/
National Inventory of Architectural Heritage - http://www.buildingsofireland.ie/
Heritage Council - http://www.heritagecouncil.ie/
Geology
Geological Survey of Ireland - http://www.gsi.ie/Publications+and+Data/Digital+Data/
Irish Cave Database - http://www.ubss.org.uk/irishcaves/irishcaves.php
National Soils Database - http://erc.epa.ie/nsdb/index.jsp
Peatland Maps - http://www.ucd.ie/eacollege/biosystems/staff/research/johnconnolly/publications/
Marine
Marine Institute - http://www.marine.ie/home/publicationsdata/
Marine Irish Digital Atlas - http://mida.ucc.ie/contents.htm
Other
Environmental Protection Agency Maps - http://gis.epa.ie/
All-Ireland Research Observatory - http://www.airo.ie/