Canoe Association of Northern Ireland website - the official Association for Northern Ireland, affiliated to the BCU.
Irish Canoe Union's website - the official Association for Ireland. Affiliated to the International and European Canoe Federations
The Irish Sea Kayaking Association has an informative site and "independently represents sea-kayaking in Ireland".
Bing Maps will help you find places mentioned.
Planning your first multi-day trip? Mark Rainsley's article "a Special Kind of Freedom" is essential reading.
Anyone planning to kayak from Scotland to Northern Ireland might find this information and annotated images, from local paddler and Postman, John Ruston, extremely useful indeed.
"Easy Reference Sheet" - Scotland - (includes Belfast's operating area). Summary sheet with paddling speed calculators, wind speed chart, CG contact & MSI Broadcast Times, Marine VHF channels etc. Specific MSI and VHF details for Ireland are in this PDF produced by John Rushton - it prints at A4 and then folds up for laminating.
Ireland - Oileain, the Guide to the Irish Islands (in various forms, including a most excellent guidebook)
Great Sea Caves of Antrim - astonishing site with fascinating images from Northern Ireland.
Photography - The Geograph project aims to collect geographically representative photographs and information for every square kilometre of Great Britain and Ireland - there are some useful coastal shots.
The entire coastline of the Irish Republic is now available online with continuous oblique helicopter photography (can be viewed as a slide show). Excellent!