This is hands down the coolest little application that I've seen in a long while. iConcertCal is an iTunes plugin, that you can download and install simply, which scans the music folder on your hard drive, then coordinates with Ticketmaster and other online ticketing sites as well as specific venues themselves, and displays a calendar of upcoming concerts in your area! And it all works in the iTunes window!!
It seems to work very well, although I've only tried it here at the office, I've already found a few newer shows that I didn't know about. I did try manual adding a few names of bands that weren't already on the crawlers search list (because that music's not on my work computer), but I'm not sure if it worked or not as nothing new showed up. It's not a super advanced program or anything, I just like it when someone comes along and uses technology to complete the obvious connections. This is a great little tool, and I'm sure it will get even more functional as times goes on. Seriously, I don't know why Apple isn't doing this themselves and then selling you the tickets directly. I'm sure they could make a tidy profit. But then again, they'd probably overcharge, and I bet something like that is already in the works anyhow.
Go check this out. It's really a great little plugin, its free, and I don't think you'll regret getting it.