For a while now I have been maintaining a Google Calendar that keeps track of various FOSS release schedules. The currently monitored projects are:
Other projects that I don't follow as closely or don't have well-defined dates (End of November isn't specific enough, OpenOffice) may occasionally be added if I check (KOffice & OpenOffice have a few entries ATM). I update the calendar on the first Saturday of the month.
If there are other projects with a good schedule page that you would like to see tracked on this calendar, let me know.