This calendar plugin worked mostly as advertised (I was not able to get the variant having no shortcode to work, but otherwise fine). But all events have start/stop times and the default UI isn't great, but changeable with CSS, of course. I tried another, MyCalendar and it has far more options and seems more configurable -- in some casess, this plugin might be all you need, but for my case, the other was far more flexible.

http://wordpress.org/extend/plugins/cgm-event-calendar/