At EVO we use memcached during every project in one way or another. We needed an easy to use interface to view a list of keys that are currently present during development.
After a bit of searching, I found this blog post describing how to interface with memcached over standard telnet.
This method is still somewhat manual because of the recursion necessary to actually view the key names, so I put together a python interface to easily grab the list of keys:
python-memcached-stats on github
Usage is simple and works on any system that has python installed (including mac OSX)