Mouse Without Borders is probably one of the most simplest but at the same time niftiest tool out there for people with more than one computer in the same place.
This sweet little utility allows you to seamlessly use only one set of mouse and keyboard across multiple computers, up to 4 to be exact. The utility does a lot more than just using one set of mouse and keyboard across multiple computers, it also has drag and drop file support, clipboard sharing for simple copy and pasting and the ability to lock and unlock all the connected PCs.
The utility is only 1.1MB in file size. It has to be installed on all the computers which you wish to connect and then you connect them all up over your local network. It's best to used a wired connection on all computers to produce the best lag free results.
This will no doubt clean up your desktop but also make you more productive. It will mean you have more computing power at your disposal while only having to use one set of mouse and keyboard.
It is Windows only and will probably stay Windows only because it was made by a Microsoft employee.
I can't wait to actually use this utility when I have multiple computers in one workspace.