I enjoy going to concerts, but I always seem to miss the ones that I really want to see. It seemed like a great website idea so I checked to see if it was already taken. Of course it was. At least I'll have some good music to listen to while I await my next million dollar idea.
There are a couple out there, but I've had the best luck with LiveNation.com. Once you sign up for a free account, you enter in all the artists you're interested in. If you are an iTunes user, there looks to be some way to import directly from there.
Now that I have about 30-40 artists in the system, I can view a calendar of upcoming concerts around me. You can also enable email alerts for new concerts. There is so much great music out there. This looks like a good way to keep track of the parts that apply to you.