I recently subscribed to the Reds Home Game Schedule using Google Calendar. Today I noticed a cool feature: they update the games that have finished with the scores, so you can see at a glance how the Reds are doing. For example, the event for yesterday was called "NY Mets at Cincinnati" but now it has changed to "NY Mets 6 - Cincinnati 8". Use this url right here:
http://mlb.mlb.com/soa/ical/schedule.ics?home_team_id=113&season=2009
Put that url into Google Calendar to see what I mean. That's the url for home games, but if you want the complete schedule or the away schedule, you can get iCalendar feeds for those too at their page on mlb.com.
Update: I'm going to attempt to embed the calendar below: