One example is Mini Explorer, which substitutes the default Windows file explorer while consuming way less memory.
You can still perform all of the normal file explorer actions, like copy, paste, rename, delete, and see properties. You can also arrange them using different filters.
One thing offered by Mini Explorer that you won't find in the default Windows explorer is the ability to change your icon theme with just a couple clicks. Choose between icons from various versions of Windows (XP, 95, or Vista) and Linux.