Delta Airlines, United Airlines and US Airways are offering cheap flights from Dublin to the US West Coast for €468 / £381 & up - round trip incl. taxes.
You can book flights from Dublin to San Francisco for €468, Seattle €468, Los Angeles €475 or Las Vegas €468. Other destinations might also work.
The travel period for this fares is until the end of September 2013. You have to book by 22nd January 2013.
If you're looking for an connection flight to and from Dublin Airport, please check Skyscanner.net.