The Project Akita OS (Orange OS) was started with the intent to design a lightweight operating system. It contains a small kernel designed for those interested in the low-level, practical aspects of building an x86 system. The host development environment is designed to work around the Bochs x86 emulator, so that you can easily test changes to the kernel.
Spiritbot is a suite of agent/bot applications with an IRC core. The core component interacts with a natural language chat interface (Scheme/LISP) base that parses input natural language (chat) input and then tries to come up with valid responses. The focus of the chat centers on technology.