If you're from outside EU / EEA and are looking to startup something, this might be helpful:

http://www.citizensinformation.ie/en/employment/types_of_emp...

http://www.enterprise-ireland.com/en/Start-a-Business-in-Ire...

If you're looking to work, you need a company to sponsor you, there's a green card programme, and in practice, it's not that difficult to get in if you're a programmer with a CS degree or equivalent experience. Sure there are forms and red tape... but it's not as many hoops to jump through as moving to the US.

More info on work visas / green cards for Ireland here: http://www.citizensinformation.ie/en/employment/migrant_work...