Perhaps the greatest single productivity-boosting feature in Linux is the ability to open several virtual desktops at one time. This allows you to create separate work environments for various simultaneous tasks, such as one with a word processor, image editor, and spreadsheet open for creating a report, and another with e-mail and browser windows active for keeping in touch with co-workers. The multiple desktops let you focus on the task at hand without interruption, but switch to your other active workspace with a single click.
By default, the Gnome interface used by Ubuntu 7.10 allows only two virtual desktops at one time, though this number can be increased to as many as 36. To add more desktops, right-click the Workplace Switcher icon in the bottom-right corner of the Gnome desktop and choose Preferences. (If you don't see the Workplace Switcher icon, right-click the panel, choose Add to Panel, and click Workplace Switcher in the Desktop & Windows section. You may also want to add the Window Selector applet, which offers another option for switching between your open workspaces.)
Make sure "Show all workspaces in (blank) rows" is selected, and set the number of rows you want the workspace-icons to appear in. Click the up arrow in the "Number of workspaces" field to add more workspaces, or simply enter a number up to 36. Click one of the entries under "Workspace names" twice slowly (but don't double-click) to rename it, and check "Show workspace names in switcher" to add the name to its panel icon. When you're done, click Close.
Move to another desktop by clicking its icon in the panel, or click the Window Selector and choose the one you want to open. You can also press Ctrl and scroll your mouse wheel to navigate from workspace to workspace, or right-click the title bar of an open application and choose one of the "Move" options. To show the program in all workspaces, select Always on Visible Workspace.
You get more ways to customize and access your virtual desktops in KDE, Compiz, and other Linux interfaces, including the ability to change the desktop wallpaper for each environment, and to switch workspaces by pressing Ctrl-Tab. There are lots of discussion on Linux forums about the pros and cons of various interfaces, but the consensus appears to be that Gnome is the most generic and least troublesome for new users. Since I'm still in that camp, I'll stick with Gnome for now, but I'm wondering whether the extra features might be worth the risk...eventually.
Tomorrow: freeware adds Linux-like virtual desktops to Windows.