How many dollors would you have need to get 8 euros?

According to google's foreign currency converter today ... December 30, 2009 ...

the value of one Euro today is US$1.4351.

At that rate, in order to buy 8 Euros, you need (8 x 1.4351) = $ 11.49 .

(Don't forget that whoever changes your money will also want a fee for doing it.)