If the person working from home has a dedicated computer residing at the office, then GoToMyPC, LogMeIn or TightVNC may work. The drawback here is security. In the typical setup for these applications, there is no centralized control of user accounts so the individual employee has complete control over access to your corporate network. If an employee leaves a password written on a piece of paper at a coffee shop, anyone can access your corporate data undetected.
For tighter control, security and oversight of user accounts and for situations where there is not a dedicated computer in the office for each person who is working from home, I suggest Citrix or Terminal Server. These two solutions require a dedicated server in your office and a knowledgeable technology consultant to set them up, however, you'll have more control over company information and access to your corporate network.