We have to build a store locator feature in our website. Wanted to check if there are any implementations for the same already available that can be leveraged.
A "store locator" feature is rather broad since this might be something you just display results on a locator page with the integration happening during or sometime after publish. Do you already have the geo-location information and/or addresses?
If you want CMS authors to select and enter this data, the SDL Tridion R5.3/2009 Google Maps extension by Frank van Puffelen, is a good example of how a Custom Url approach can allow authors the ability to select items through a Google map.
For SDL Tridion 2011, you would want to consider updating something similar to Google Maps latest API (version 3, I believe) along with using the latest Custom Url pop-up script.
If you find something else or start a new version based on the existing setup, do consider contributing maybe parts of it back to SDL Tridion World.