I added some quick hacky iCal support to the upcoming meetups sidebar here on MetaTalk. Hit the "iCal" link to get a properly formatted calendar file you can subscribe to and see all the upcoming meetups in your calendar of choice. Here's what it looks like in iCal.
Sorry to be posting again so soon, but, pursuant to Smart Dalek's request, I've put together a little calendar of upcoming MetaFilter events in iCal format. Nothing too fancy, just me manually adding events to the calendar as I receive them. Nothing is on the calendar yet, so submit something, already. Details on subscribing to (if you use iCal on Mac OS X 10.2.1 or later) or viewing the calendar are here. Hope you like it.