MagiCal | Software | Charcoal Design
http://www.charcoaldesign.co.uk/magical
"MagiCal is a FREE menu-based clock and calendar. It features a huge range of configuration options for how the time and date are displayed, and can operate either in conjunction with, or as a replacement for the built in system menu clock."
iCalendar package for Python
http://codespeak.net/icalendar
"The iCalendar package is a parser/generator of iCalender files for use with Python."