To get to a specific drive/directory without drilling down with the mouse, select Tools | GoTo (or press <CTRL><G>), and type the desired path.
To see how much space is available and used on each logical drive on your system, click on the Computer name just below Desktop in the left pane. The right pane will list all of the logical drives with total size and free space.
To see the number & size of the folders in any logical drive or folder, select it and then right-click on it and select Properties. Drives will show a pie chart while folders will show the number and size of files and folders.
Most of the following tips assume that the Explorer window highlight is in the right window pane. To get the window highlight there, either press <TAB>, or left click anywhere in the pane.
To select a file or folder, press the first letter of what you want, or use the cursor keys.
To select multiple non-contiguous items, hold <CTRL>, use the cursor keys, press <SPACE> to select/deselect.
To delete the selected item(s) and place them in the Recycle bin, press <DELETE>.To delete the selected item(s) without placing them in the Recycle bin, press <SHIFT><DELETE>.
To open a file into an application other than the one normally associated with it, hold down <SHIFT> as you right click it, then choose OpenWith.., and then select the desired application. If it's not listed, click Other to browse.
Want to select every file in a folder but one? Or every one but two or three? Windows 95's Invert Selection command takes the tedium out of file selection. With a folder window open, select the file(s) you don't want, then pull down the Edit command and choose Invert Selection. When you let go, everything that wasn't selected now is, and the files (or file) you had selected are left out completely. The Invert Selection command is available in any Explorer window, too. Just select the files you don't want in the right pane, then choose Invert Selection under Edit to reverse your selection.