mongoPHP
mongoPHP is a simple PHP based MongoDB administration tool based on the GAS Framework. It is completely open source and maintained by Simon Fletcher (http://twitter.com/simonify).
Getting Started
Once you have uploaded the files you will need to edit the site.xml file within the /_application/configs/ directory. You will need to change the mongo address value to your real MongoDB server's URL. Once this is done, you're good to go. Oh and you may also need to alter the value of the path node within <application> (if you do not upload the files to http://yoursite.com/mongo/).