Valid passports are good enough to enter Ireland for citizens of Australia, Canada, New Zealand, the UK, the US, and South Africa. Money Legal tender in Ireland is currently the Irish pound, but that will soon give way to the mighty Euro.
Bank machines are all over the place, and creditcards and traveller's cheques are widely accepted.
Communication Phone cards are popular among the backpacker types in Ireland. They can be found at most corner stores and are either dialed in, or inserted into the phone itself. The international dialing prefix is 00, and the country code is 353. For a cheap alternative to phone calls, head to an internet cafe and email home. Cafes are all over Ireland, and many hostels have computers you can use for a fee.