geo-autocomplete converts any input field on a web page into an autocomplete field that suggests locations in real-time as you type, including a little thumbnail to help you quickly choose the right location. It's like Google Instant for your Maps.
UPDATE, AUGUST 2011: The Google Maps V3 API now incudes an autocomplete feature that will adapt any text input field to autocomplete locations &/or Places. It doesn't show thumbnails yet but the addition of Places will be great for some use cases, here's the details:
if you still want the thumbnails, or if you like jQuery want to use it to tweak the behaviour of the geo-autocomplete field, this jQuery plugin might still be useful for you -
A thumbnail of each suggested location is also presented, using the Google Static Maps API v2, to help you quickly choose the right location.
You can use all the standard jQuery UI css and Autocomplete options to customize the look and behaviour of your geo-autocomplete field, plus some additional options are available, inspired by frequently requested features:
geo-autocomplete is now built upon the jQuery UI framework as a jQuery UI widget, rather than a jQuery plugin.
See ui.demo.html for some demos.
The previous version, an extension to Jörn Zaefferer's excellent Autocomplete plugin is still included if you want that one.