There's a fairly new site on the Web called BookTour.com. I've just spent some time checking out the site, and it looks like a really great tool for bringing authors and readers together.

Basically, this site serves as a central warehouse of dates and times for author appearances and book tours. It uses a simple to navigate interface for people to find your events anywhere in the US, UK, Australia, and Canada. If you're doing a national tour, this could be a useful site for promotional purposes.

The only caveat is that you actually need to go to the site and input your travel schedule manually. However, in the big scheme of things, it's only a little extra work that could payoff by bringing people to your appearances.

Cheers!
Erin