ODesk, Elance, Vworker, Freelancer.com and Guru are freelancing sites that facilitate and streamline the process of hiring virtual (or remote workers).
Each of these sites have their own approach, but in essence, all of these companies allow you to do more or less the same thing.
You can post a job description, have people bid on the work, negotiate on price, and look at previous ratings and work history before settling on either a contract rate, or a pay-per hour agreement.
Generally, money is escrowed (or held) by each of the websites and they release the payment to the worker when the work is complete (skimming a neat profit at the same time – typically 10-15% of money that changes hands). Find out more