Recently, Apple enabled CalDAV subscriptions on the iPhone (which also play well with Google Calendar); that made me dust off my copy of iCal and take a second look. If you're not using iCal at all, you may want to take a moment to learn about what you can do with it.
The idea of calendar subscriptions is simple: store a calendar event database somewhere online, and then provide a link in a common format for calendar programs such as iCal to access. The calendar program then imports the calendar data and puts it in your calendar, updating itself at a frequency of your choosing.
Online databases of public calendar links abound, and you can add calendars from your local little league schedule to stargazing guides to the galaxy in your area. The format that Apple uses is the "ics" format, and you'll see calendars with that extension all over the web.