You can get notified about new events using one of the subscription mechanisms:
iCalendar Feed: If your calendar supports calendar subscriptions, you can add a calendar feed. Thunderbird Lightning, Apple Calendar, Fastmail and Google Calendar are known to be working.
RSS: For users of feed readers, Atom/RSS 2.0 feeds are available.
Twitter: The calendar tweets about all new events as @osm_events.
If you experience compatibility problems, feel free to report them.