U.S. Customs and Border Protection recently announced the availability of the Electronic System for Travel Authorisation (ESTA). This is accessible for citizens and eligible nationals of the Visa Waiver Program (VWP) countries.
Effective 12 January, 2009, all VWP travellers will be required to obtain an electronic travel authorisation prior to boarding a carrier to travel by air or sea to the U.S. under the VWP. Additional information can be found here.
To apply for the ESTA click here.
*Please note if you are holding a non-machine readable passport, you will need to obtain a visa from your local United States Embassy.