You can integrate your MindMeister tasks to your favorite calendar application(s) and keep track of milestones, project dates, etc.
You can enable the Task Feeds in your Settings and choose between several feeds.
Once you enabled task feeds in MindMeister, all you have to do is copy the URL in your calendar app. If you're using Google Calendars see the screenshot below:
If you're using iCal see here: