look up a phone number in Ireland

What is the best website to look up residential numbers in Ireland, particulary Dublin? Thanks so much.

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Go to eircom.net. Then click on the link for Phonebook on the left. 

To call: 
The country code for Ireland is 353 
The city code for Dublin is 1 
A Dubin phone number has 7 digits in it. 

So if calling from outside of Ireland the way the phone number is dialed is: 
your countries international dialing code 353 1 XXX XXXX 

E.g. if you are calling Dublin from the states the you dial 011 353 1 XXX XXXX 

Hope this helps!