There are lots of different tools on the market that can help monitor email, stop USB ports being used, or control printing. However, the tools listed below are designed to combat all the different threats from Data Loss Prevention, in a single tool. Therefore thess tools are big, impressive, and expensive.
Vontu (now owned by Symantec): This is a huge tool that plugs into your network and monitors data loss from a variety of systems, including the USB ports. This is not a cheap and cheerful tool, but one for blue chip companies. It works, like others in the same market space, by monitoring what data you have, and then allows you to classify either single files or entire databases as confidential. The tool can then stop “confidential” data, depending on the users permissions, from being copied out of the company. E.g the CEO may be able to email the company financials out of the company (e.g to an ccountant), but not copy it to USB drive, but a junior account could only access to the file not copy or email it out.
Websense: Like Vontu above this is a high end tool that connects to all your data bases, so it understands your data, and then prevents data loss by monitoring all ports and applications for key data leaving the company via any of those processes – e.g email, IM, USB ports.
McAfee: Another premier league tool. This is also designed to monitor and stop data leaks from a variety of different sources – including USB, email and IM.