I get asked frequently how I incorporate calendars and event lists into some of the websites that I design. It’s really pretty simple after you’ve worked through the process once. I use CalendarHub for event lists (it’s free!), I was using Trumba for MonticelloLive’s community calendar (a paid service, but full of features). Recently, I’ve been using Airset for several projects, especially for coordinating a calendar with lots of folks. It works great for church use, but its learning curve for the casual user is steep. It’s not very intuitive (aka, very un-Maclike).
Here’s an excellent article on dozens of other online calendar options out there.
Here’s an article related to this that I wrote a while back.