If you are travelling to the US from a visa waiver country like Australia you need to fill out a ESTA form online (has been like this for a couple of years I think). You do it once and you're good for the next couple of years and you don't need any specific details like flight numbers or whatever, just your passport numbers. If you do it from after the 8th (ie after tomorrow), they'll be charging $14 US, so really no reason not to quickly fill one out tonight!
Some links to new fees to be implemented:
https://help.cbp.gov/app/answers/detail/a_id/1193/~/esta-fee…
http://boardingarea.com/blogs/theglobaltraveller/2010/08/us-…
Thanks for the heads-up.
However, looks like the site isn't coping too well :(