SPIN

What is SPIN?

SPIN is an operating system under development at the University of Washington designed with three goals in mind:

Flexibility: Ordinary users are allowed to customize SPIN by writing extensions to the kernel, which can be dynamically linked into the kernel's address space while the OS is running. SPIN applications can exist entirely in user-level address spaces, entirely as extensions in kernel-level address spaces, or partially in both.
Safety: SPIN and its extensions are written in Modula-3. It relies on Modula-3's type-safe properties to protect sensitive kernel data and interfaces from users trying to construct malicious or errant extensions.
Performance: The flexible structure of SPIN allows programs to extend operating system services with low overhead. Application-specific extensions can access system resources and services with low latency since there are no expensive protection boundaries to cross within the kernel.

A good place to look is the SPIN Home Page.

Check out the SPIN Research Projects Page to find out what cool development is being done based on SPIN.