I have been making a managed library for the OpenZDK, meaning it will be possible to use things such as the keyboard and networking functions of the ZuneHD through C#. As various people have pointed out, this approach is relatively slow compared to using C++ and C. However; if you're interested,
here's the download link. It can now no longer requires the IDWOS, so it can be ran and compiled without having to use my boring-looking shell. It's not really anything new, but it's just a simpler way to take advantage of the Zune's keyboard right now, and it currently does not support networking; however this feature will be added soon.
Also; anyone using this development kit can post their apps to this thread. I'd like to see what people are doing with this kit, and improve it if necessary
UPDATE: Networking capabilities coming soon - An updated library will be released when I publish IDWOS 2011 for ZuneHD (maybe even before then)
Edit: Please be sure to follow all of the instructions and follow them in the order described on the download page.