The USA is going to start charging current Visa Waiver passport holders $14 to apply for their ESTA to travel to the USA.
The ESTA is required for all air and sea travel. You do not need one for land crossings (e.g. from Canada). If you currently fill out one of the green I-94w forms on your way into the states then this affects you!
The fee kicks in on September 8th 2010. If you apply (or re-apply) before then you get TWO YEARS for FREE!
The official ESTA site (beware the fakes!) is here: https://esta.cbp.dhs.gov/
More info here: http://bit.ly/a2HWLI
So if your British, European, Aussie or Kiwi.... it probably wouldn't hurt to apply anyway now!