Songkick
Tries to create a comprehensive listing of all the concerts in your area. Too much ajax. Also take a look at Sonic Living for another comprehensive list.
I'm one of the people behind Plancast.com. Our goal is to make it easy for you to share your plans. Maybe you read about us on Techcrunch or ReadWriteWeb?
My Plans: Plancast.com
My Notes: Noopsi.com
My Tweets: Twitter.com
My Code: Github.com