VirtuaWin is a virtual desktop manager that lets you have multiple "desktops", helping to organize your life. For example, you can have one desktop for work and one for play, and instead of having a ton of windows open in one desktop, you can divide them up into two. It also helps you keep focused.
I'm not going to lie, other OSes (Linux, notably) have a strong emphasis on virtual desktops, so much so that they are often built in. But Windows users may not be familiar with the idea, and may therefore be less likely to try it. But I would suggest giving virtual desktops a try, even if they sound odd or perplexing, because they just might very well change how you use a computer.
The first nice thing about VirtuaWin is the layout of the desktops. By that, I mean, you can set it up to be "3 wide, 1 deep", or "2 deep, 4 wide", meaning you will have a "grid" of virtual desktops. I myself prefer to have just a line that I can switch between, left-right style, but if you so desire to have a 3x3 grid of nine desktops, that usabilty is there for you. You can also name your desktops, so you can distinguish what windows go to what (like my earlier example, "Work" and "Play" could be your desktop names).
You can also configure how to handle when windows pop up (like switching to the desktop where the window is, or bringing the window to the desktop you're on), and configure what options you want to be accessible in your tray menu. Speaking of options...
Options! On top of having different windows on different desktops, you can also use nice tray options like "Switch to" a specific window, "Move here" to move a window to the current desktop, and "Always show" which makes a window follow you wherever you go.
VirtuaWin also has the very, very nice tool of hotkeys, meaning that you can navigate through your grid of desktops just by pressing a key. You can set them to be almost whatever you want, and the actions you can use for the hotkey are vast.
VirtuaWin also allows you to use your mouse, like dragging the window to the right of the screen will move it to the next desktop on the grid. And of course there are too many options for me to list for this as well.
If VirtuaWin wasn't amazing enough, you can also download modules, which allow many different enhancements (like having a panoramic wallpaper spread across your virtual desktops, for example.)
VirtuaWin has a lot of options for such a small program. It's only around 200kb in size, runs around 6mb, and is completely portable, in case you wan't to take virtual desktops on the go. It's also open source, if anyone wants to take a peek at how it works.
The only slightly bad thing about VirtuaWin is that it is so configurable, it might scare those who are not used to virtual desktops. It might not be the best choice for someone who has never used a virtual desktop program before, but if you have and you want customibility, then VirtuaWin is for you.