Here is a great Google Maps plugin created with the Google Maps API that can geolocate visitors to your blog and plot it on a nifty little Google Map for them! Head over to this blog to see it in action. The plugin geolocates the user via the whois data that is attached to their ip address. For comprehensive instructions on setting this up on your blog and a link to download the plugin itself, check here. Even if you don't have a blog or want to set it up, be sure to check out this blog to see how accurate it is for your location!
Here is a screenshot:
(Get this plugin here..)