EventCalendar 3.0 is a great WP1.5.2 plugin that displays future events in both calendar and list formats. Simply create a post, change the date to some day in the future, and add it to your event category, and it will be displayed with a neat mouseover tool tip. Clicking the event takes you to the post on that event, even if it’s still in the future (WordPress normally doesn’t display posts with a future timestamp).
Unfortunately, the event list doesn’t work in WP2.0. The calendar works great, though, and you may find it very useful.