I've tried most of them, and eventually settled on filethingie a single drop in php file.
http://www.solitude.dk/filethingie/It's very easy to rename files, change the css (expanded version), move files, upload files. lots of settings.
Although I should also mention Phpfm (PhpFileManager) it has pretty much the same functionality also in a single php file. It also has multi-select which is nice if you need to move a lot of files around.
The only drawback is that it's a little harder to rename files.
http://phpfm.sourceforge.net/They are both very useful and well made. One thing I should also mention is if you are using a new version of PHP, Phpfm's index file begins with <? instead of <?php - you will need to change this if you do not wish to force backwards compatibility in php.ini