An interesting announcment was made yesterday of Microsoft's intention to acquire a product named "i:filter" from a company named Futuresoft.
i:filter enables you to control the internet surfing habits of users on your corporate network.
Your policy can specify which URLs can be accessed taking into account the time of day so you could enable social browsing out of working hours.
URLs are clustered into categories such as "Shopping" and "Travel" enabling you to easily specify the permitted destinations. According to Futuresoft's website the product one of the largest content filter databases on the market with over nine million destinations.
i:filter already integrates with Microsoft ISA Server to provide seamless content inspection at the network boundary. The product can also be installed independantly of ISA. The product comprises three components namely one or more network monitors, a management console, and central database.
The Futuresoft website includes many more details including a statement for existing customers. The website includes plenty of documentation together with a product tour and quite a good reviewer's guide.