I started this project as a convenient way to interact with the Switch over the network. Simply run the provided .nro file included in this post and connect to your device via port 5050 to access a Unix-esque shell. A full list of currently-supported commands can be provided by typing "help" at the prompt.
For more information, or to report a bug, check out the project on GitHub:
First ensure that you have the "telnet" client installed on your local machine (it may or may not be bundled with your base distribution). For Mac users, I recommend installing the client via the Homebrew package manager. Then, connect in via:
$ telnet [IP address] 5050
The built-in Windows telnet client does not play nicely with nxsh, so I recommend installing PuTTY. Note that connecting via a "raw" connection instead of a "telnet" one will avoid a pesky "command not found" message upon initialization of the shell. The telnet protocol sends some garbage text as it's negotiating the connection, so if you want a clean-looking shell, ditch that and go for a raw socket.
In Progress/Future Plans
Right now, there are a few big features under development. Firstly, I'm working on a set of fetch commands to retrieve files from remote HTTP/FTP servers. More ambitiously, I'm developing a shell interpreter so that basic scripts can be developed and run on the Switch, as they would under bash/zsh for example.
I'm always open to feature requests, so don't hesitate to let me know if there's something you'd like to see included in the next release!