As Overman has already mentioned, I’ve set up a Google Calendar which is intended to be specific to Machinima (and Anymation). You can subscribe to the feed for the calendar using any compatible calendaring tool, or just do a search on public calendars for “machinima” if you use Google Calendar.
You can also embed the calendar on your website or in a blog post if you’d like to. I’ve added it to the sidebar on this site.
The exact purpose and scope of the calendar is still up for debate, so if you’ve any suggestions for events or additions to the calendar, or you just want to tell me why you think it’s a good plan or a terrible plan, send an email to calendar at machinimafordummies dot com.