I've been working on a new Import/Export plugin for Cinema 4D and have just posted the first release, which can be found at Spanki's Prop Shop.
The plugin reads and writes .mesh.xml and .skeleton.xml files (including skeletal animation), with the option of converting to binary format when Exporting, using the external converter program.
The plugin is being distributed as a commercial product, but a fully functional 30-Day Trial period is available by entering DEMO as a license key. I am also offering special Introductory Pricing for a limited time.
The original thread has some additional details and somewhat of a development log, but the most up to date information can be found in the included documentation and/or by just downloading the demo and kicking the tires

EDIT: The links in this post (including the I/Ogre Product Page and User Manual) have images in them, but just so this thread has something different, here is Psionic 3D's free "Beast" figure, Imported into Cinema 4D with my up-coming MilkShape3D (.ms3d) file plugin, then Exported to Ogre .mesh/.skeleton format using the I/Ogre plugin and finally loaded into ajs' "Player Demo"...

...(note that I/Ogre doesn't currently Export any .material file - so I created a simple one by hand for the above example).
The original file had non-descriptive bone/joint names, so I renamed all of those. The original file also had separate mesh objects (submeshes) for each leg, the tongue, the eyes, etc., so I combined them all into a single mesh and re-weighted the joints before Exporting. Here's what the C4D Object manager looked like when I exported (most of the Joint branches are folded up to save room)...

...note that the (selected) Figure Export Tag is set up with specific root filenames (so it didn't use the figure's root-level object name "beast5x") and the appropriate links to the Skeleton Root Bone and Anim Clip Tag are filled in as well...

Cheers,
Keith