fplan is a freely distributable application (with source code) designed to assist general aviation pilots in creating flight plans for cross country flights in powered aircraft.
The Linux Aviation HOWTO provides pointers to software packages that run under the Linux operating system and are useful to private, commercial, or military pilots.
Apparently no longer maintained, but of interest for historical reasons. Besides a list of Usenet newsgroups, also contains links to FAQs, newsgroup descriptions, and other Usenet information.