I just "discovered" Upcoming.org today. I've known about it for some time, but I never really spent any time exploring it. I've gone about adding all sorts of events to the Kansas City metro.
If you pay any attention to the column on the right side of my web site, you'll see a new "upcoming in kc" section - that's being generated by entries on Upcoming. So go sign-up for an account and add the events you know about. With enough people adding an event or two a week, we could have all of the goings on in Kansas City covered.
Oh - and if you'd like to display what's "upcoming in kc" on your site, just leave a comment and I'll send you the code. Right now it requires a bit of technical know-how to make it happen, but if there's enough interest I could make a widget that you could just copy and paste into your site.