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Movitz - The Movitz system aspires to be an implementation of ANSI Common Lisp that targets the ubiquitous x86 PC architecture "on the metal". That is, running without any operating system or other form of software environment. Movitz is a development platform for operating system kernels, embedded, and single-purpose applications. There can potentially be several completely different operating systems built using Movitz.
FunOS - FunOS is a mostly-functional (in the programming language sense) operating system currently in design. Or alternately, it is an operating system for which it is fun to do systems programming.
(När jag ändå är igång passar jag på att länka till Christopher B. Browne's sida om Lisp-based OSes)