Bret Feddern has created a plugin that adds a sidebar widget that shows the weather based on the user's IP.
The Google Weather plugin that provides a convenient little sidebar widget for websites using Mango Blog's framework. Once activated, the plugin acts as a Pod and is controlled through a small admin screen that supplies options for display and lookup. The current weather conditions will be displayed in the site's sidebar. That includes a small thumbnail describing the conditions, the temperature (F and C), the wind and the humidity.
The Plugin uses the visitor's IP address to check Google Weather for the current conditions. For websites in the US, the plugin also allows a way to provide a static zipcode for the site to use in displaying weather conditions. This provides website owners a way to display for one specific location.
The Plugin functionality uses a few different API's to make this happen. It uses Hostip.info's API to get the city for the IP address. Hostip.info is a free, community-based project to geolocate IP addresses (http://www.hostip.info/). The Plugin also uses Monte Chan's Google Weather API function to get the weather for the city returned by Hostip.info's API. Chan's function is included in the Handler.cfc file.
You can read more and download from RIA Forge.