http://www.irishgenealogy.ie/en/
Goes up to 2013 for the Republic of Ireland and up to 1921 for Northern Ireland. It seems that births (for the Republic) go up to 1995, as far as I have been able to make out from trying it out.
When you begin your search session you will need to give your name, and then you have to complete a "Capcha" test (this is to make sure that you are not a "bot" but an actual person.)
Some of the index entries that you get in your results have a "Group Registration ID" rather than volume and page. Presumably this Group Registration ID can be used to order a certificate from the GRO Ireland.
The marriage results show spouse's name for recent years, but not for older marriages. I'm not sure at what date this changes yet. And you can search for births using mother's maiden name - just put it in the surname box (with or without the father's surname). But again, the mother's maiden name doesn't seem to be available for older records. I guess it just depends on what was on the printed index for that year.
I am quite concerned to see that the site gives the exact date of birth, even for people born in 1995. Together with their mother's maiden name. Hopefully these are not used as banking security checks in Ireland? (Yes, I realise that MMN is on the online indexes for England and Wales too, but not the exact date of birth.)