One of the most searched Keywords on my site has been for Free BMD Records for Northern Ireland. At the moment there is not a site out there offering all of these records . These are my favourite sites that offer some information but not all.
Emerald Ancestors offer a free search but to get the most from this site you have to pay for membership. At 10 pounds for one month this is really good value i have found it to have been the best site in finding results. If you have friends who are also researching Northern Ireland, then take it in turns for membership doing look ups for each other.
Ros Davies Co Down Genealogy Research site
Most people researching County Down will have used this site but if you are new to research then this site is full of records. Take the time to search through it and bookmark it .It will be a free resource that you will use constantly.