MINIX is a free UNIX clone that is available with all the source code. Due to its small size, microkernel-based design, and ample documentation, it is well suited to people who want to run a UNIX-like system on their personal computer and learn about how such systems work inside. It is possible for a person unfamiliar with operating system internals to understand nearly the entire system after just a few months use and study.
TinyScheme is a lightweight Scheme interpreter that implements as large a subset of R5RS as possible without getting very large and complicated. It is meant to be used as an embedded scripting interpreter for other programs. As such, it does not offer IDEs or extensive toolkits although it does sport a small top-level loop, included conditionally. A lot of functionality in TinyScheme is included conditionally, and it allows multiple interpreter states to coexist in the same program without any interference between them. Foreign functions in C can also be added and values can be defined in the Scheme environment.
mkpwd is a password generating program. It is designed to satisfy a scalable range of security demands. Its standard behavior is to generate one password consisting of any of all printable ASCII characters (32-128) with a length between 6 and 10. You can modify the way passwords are generated via command-line switches. You can specify a length range, the characters used, and even let mkpwd generate passwords that are somewhat readable and therefore easier to remember (and easier to crack as well).