I'm British, what is the longest Visa I can get for the USA or Australia?...wanna visit you guys!?

As British citizen you can visit the United States as tourist for up to 90 days under the Visa Waiver Program. To use this program requires a prior online authorisation (ESTA) to be obtained on the website of the U.S. Government; fee US$14 to be paid by credit card [MasterCard, VISA, American Express, and Discover (JCB, Diners Club)]. Payments can also be made with a debit card that holds the MasterCard or VISA symbol. Make sure you apply on the official government site; lots of scammers on the net who just want to phish your details.

https://esta.cbp.dhs.gov/esta/esta.html ..

For a longer stay [up to six months] you would need to get a B-2 visa, fee US$140. However it is not recommended to apply for this visa unless you can really show strong economical and social ties to the U.K. More than 25% of the B-type visa applications made in the U.K. have been refused last year, basically those of young unmarried people.

http://london.usembassy.gov/b2.html ..

For Australia you will also need an online authorisation (e-visitors) for a three months stay; the application however is free of charge.

http://www.immi.gov.au/visitors/tourist/evisitor/ ..

Again for a longer stay you would need to get a visa which can be applied for online. Fee: A$110 [£75]

http://www.immi.gov.au/visitors/tourist/676/ ..

You may visit the U.S. under the Visa Waiver Program for up to 90 days without a visa. This cannot be extended for any reason. You must register for ESTA before coming. See site below. Or, you may apply for a B-2 tourist visa, and if you can show sufficient funds, you may stay up to 6 months. However, it is very difficult to get the B-2 visa. You must show proof of having COMPELLING reasons to return home. This means MONEY...own a home, business, or have a very large amount of money in the bank. Worldwide, about 50% of applications for a B-2 visa are denied. If your application is denied, you cannot then come under the visa waiver program...you just cannot come at all. So, it is far wiser to come under the waiver program.

Tourist visa to Australia is 3 months and costs very little. The 12 months' working holiday is harder to get, and is quite expensive.

Tourist visa to US is 3 months