I've never used the calendar, either on my site or anyone else's. Although I personally think they're pretty close to useless as a navigational aid, not to mention I don't like the additional clutter in my sidebar, when I read got done reading that article (and comments) at 1976design, I remembered: call 'em blogs, call 'em portals, call 'em whatever you like, but these are still, at heart, *personal* pages. If you like it, use it! It's trivial to remove if you don't want it.
I think I like the *idea* of the calendar, but the reality is that, for me, they take up screen space and serve no useful function. Southern Gal's got a kinda neat new script on her page, a calendar that pops up a hover when there's an event on a particular day. That's theoretically more useful (in case I ever want to know what SG's doing on a given day), but practically speaking, not something I'd use either. There's lots of stuff on blogs I don't personally use or want on my blog...shoutboards, galleries, and music streamers...but now I'm curious..what (besides content) do people want to *do* on a web page? Play games? Listen to music? Look at pictures? What're your favorite 'optional items'?