Pal is a color, command-line calendar similar to gcal with support for displaying events and holidays. It supports many types of recurring events and has an easy to use interface for adding new events.
Pieman is a command-line tool for managing personal information such as appointments, contacts, and tasks as well as other data such as notes and rc files. It is a portable pure-perl tool inspired by abook, devtodo, mutt, and pal, among others.