One of the most often sought plugins from my experience, after a photo gallery type one, is a coming events/calendar type plugin. This one offers another option. Though it doesn’t seem to link into the calendar specifically, it allows you to create a special category for coming events, and list them in your sidebar.
The twist to this plugin is that it converts that category feed into an ical type feed that then allows people to subscribe to it in any calendar application that supports the ical protocol, which includes google calendar. That I think is a very nifty feature, and one that I believe many will find useful for WP powered sites that are used for projects, communities, and the like.