Not a plugin, however you can easily embed a functioning Google Calendar in a post or a specific static Calendar Page.

Example only Cal in a post:
Toogle back to January for some entries :)
http://wow-factor.com/index.php/calendar-test

Looks nice.

That would be good if we can sticky it, perhaps.

Or just have specific Category for Calendar
It's most likely best displayed on a specific "Calendar" page that can maximise it's width and therefore the entries.

It's a bit too tight on my skinny skin.

Or make it be the only post on a blog that uses a skin with no sidebar, thus allowing full width to the calendar?

(Was just thinking "wow I could use that as the only post on a blog with a full width skin" so there you go ;) )

Ed,

It is quite a coincidence that your thought happened to be the solution to my problem.

Check http://doodle.com/
It's a great way to share and schedule event.