A customer recently asked me what the best way was to create a web part (quickly) that showed the contents of a remote file share. Well, the answer is quite simple.  Simply drop a Page Viewer web part on your page, select Folder as the source, and then enter the UNC path to the file share (for example, \\servername\fileshare).

You'll get a very slick web part on your page.  It has a couple of limitations, but it's great for a quick “file viewer“ web part.