Spaces, the virtual desktops built-in to Mac OS X, are great for organising your open apps and separating the ones you want to focus on from the distractions. In previous versions of OS X, you aren't able to organise or rearrange them, but in the latest update to Lion, 10.7.2, rearranging Spaces desktops is as simple as dragging and dropping.
The new feature appeared in last week's 10.7.2 update, which also added support for iCloud and Find My Mac. To rearrange your desktops, open the Mission Control view by clicking its icon in the dock or swiping three fingers upward on your Mac laptop's trackpad. Then just click and hold any of the desktops across the top of the screen and drag it into the order you'd like.
In previous versions of OS X, Spaces desktops were organised in order of most recently accessed. Your current desktop was first, the last one you were on was second, and so on. The same is true in the update, but at least now you can tweak the order and it'll stick.
How to Rearrange Spaces in OS X Lion [Business Insider]