Any type of manufacturing process, research, accounting, payroll, legal, etc.
There are so many companies that offer temp services or contractor services. (Manpower and Accountemps are two that come into mind)
Most of these companies have already done the recruiting and have people ready and waiting for their next assignment. Also, if your company doesn't 'like' the person you received, you can actually request another person and it'll cost you nothing more. Plus - your company will save benefit costs by utilizing an outside service instead of directly hiring a person. If you decide afterwards that you want this person to stay on with your company, it's just a matter of making a deal with the outsourcing company.