Jay Marcyes

Any push to standardize iCalendar is good in my book, also check out this post (and the whole blog) for more calendar standardization/validation discussion.

by far the best write-up (with lots of examples) on how the iCalendar recurrence format is set up.

An open source iCal creator. Coincidentally, ICal has my vote for one of the worst specs in the history of specs. Here is the RFC that spells it all out. Here is another reference I liked. And of course, Wikipedia.