Upload-to-cf-cs is a project mainly written in C#, it's free.
Upload to Rackspace Cloud Files in C#
This is a very simple C# binary to upload a file to Rackspace Cloud Files.
Build:
Windows: install nant http://nant.sourceforge.net/ and run nant.exe in the directory
Linux (mono):
apt-get install nant (or other method of your distro but that will work for sure in debian/ubuntu).
nant on the source directory
Run:
Syntax is simple as :
UploadToCFCLI.exe $RCLOUD_API_USER $RCLOUD_API_KEY ${CONTAINER_TO_UPLOAD} ${FILE_TO_UPLOAD}
This is straightfoward enough to don't need a long README.