Snowbox is a small and easy-to-set-up POP3 server. It supports APOP, SSL, and IPv6.
GoESMTP is a multi-node ESMTP server. It was designed from the start to work as a cluster. Each node keeps an index of the available messages by using hashes which are distributed throughout the cluster.
A Python library that lets you to define, optimize, and evaluate mathematical expressions involving multi-dimensional arrays.
A personal finance manager.