I want to view/edit a file on my disk, but I don't want to set up a project for it. Is there a way to open random files?
Yes, there is. The simplest way is to select File > Open (Ctrl-O) in the menu and select the file you want to view/edit. Or, you can open the Favorites view (Ctrl-3), right-click and select Add to Favorites to add whatever folder you want to make available for browsing. Then you can navigate around the tree of files under the selected folder and open, rename, copy, move them as you like.
Note that the latter approach is very similar to the concept of filesystem mounting known from the NetBeans 3.x series. However, the Favorites view, while useful for quick file navigation and simple file operations, is not meant to be used for regular project related work. That's what Projects and Files views are for.
Applies to: NetBeans 4.x, 5.x, 6.x