Warning: This plugin is now hosted on GitHub: https://github.com/thegcat/redmine_ical
Redmine Ical aims to provide an ical/ics feed or export of issues and versions to be imported into/subscribed from a calendaring software.
This plugin is originally based on the Redmics Plugin, but is a near-complete rework to use existing redmine facilities instead of an extra implementation. This also allows one to use custom queries already defined for issues for the calendar, though redmine is still lacking on the UI side to fully support this.
Please understand that the current version is usable but a work in progress.