Colorado Startups has created an events calendar.
As you might have guessed, there are lots of interesting events happening in the Denver-Boulder area but finding out about them is sometimes a little difficult. Having someone find and aggregate that information into a single calendar is immensely helpful.
They are using Google Calendar as the host of the information which means that you can subscript to the calender with RSS or include it in any other calenders you might already have. I really like that second option as started keeping track of my schedule in Google Calendar already.