IncludeOS is an includable, minimal unikernel operating system for C++ services running in the cloud. We provide a bootloader, standard libraries and the build- and deployment system. You just provide the service.
Test in VirtualBox or QEMU, and deploy your service on OpenStack.
Read about IncludeOS in InfoWorld, listen to a podcast about IncludeOS or read IncludeOS: A Minimal, Resource Efficient Unikernel for Cloud Services.
Everyting is on GitHub: Just follow the simple installation instructions, and you will be writing your first service in no time. You can also read the documentation and look at known issues and feature requests.
If you want a command line interface, there is support for IncludeOS unikernels in UniK, the Unikernel Compilation and Deployment Platform from EMC.