DisplayFusion - DisplayFusion will make your multi-monitor life much easier.
Synergy - Cross-platform software for sharing your mouse and keyboard between multiple computers
Preme for Windows - Speeds up your window switching.
Input Director - Control multiple windows systems with one keyboard/mouse. Share a keyboard and mouse across multiple windows system.
GridMove - GridMove - A window management tool that can quickly arrange your windows into desktop grids.
Ultramon - UltraMon is a piece of software built to help with the management of multiple screens on the same computer system. Without software like this, taking full advantage of an expanded desktop space can be difficult.