Here is a crazy idea.
Every website that has events should publish an ical file. Just like they publish RSS, they should publish their events based on dates. ICS files with VCALENDAR entries are easy to publish.
Today when I look in my browser it looks in the header for a line that looks like this:
<link rel="alternate" type="application/rss+xml" title="RSS" href="http://tangent.org/index.pl?node=rss" />
I want to see something like the above with calendaring information. I can subscribe to it, so therefor I want my browser to auto discover it.
Calendaring is more then just shoving it into a database, its about finding events and being alerted to them.
And no, don't just put the events into RSS since my calendaring program doesn't know RSS, it knows about calendaring formats.
Sure my Calendar ought to know how to take a part an RSS stream filled with events but that is another story.
PS: Do vCard entries on all profiles while you are at it :)