San Diego Trolley Map - This Google Maps transit mashup takes an independent ride-guide for the San Diego Trolley and mashes it up with Google Maps. It even includes a .kmz version for Google Earth as well. This website, blog and mashup is a great example of how Google Maps and Earth are empowering a new breed of web 2.0 "indy transit" sites. I like this quote from his blog: "No more visits to badly-designed websites to find out when and where to go." (More transit mashups here..)
Other new US Google Maps Mashups:
San Francisco Shopping Map - Platial map with video and interviews with shop owners. Here is an example location from the map.
Bicycle Trip Planner for Portland, Oregon - Is also available for Portland, OR, Milwaukee, WI, and Pittsburgh, PA.
Santa Clara Bike Maps
Board Game Stores in the US
New Real Estate Search
SimplyVermont.com + Google Maps - Vermont businesses, local attractions and points of interest on a Google Map
St.Paul's List - Created by Ning.com - More information is here.