(Warning: Initially I resisted posting this mashup when it was suggested to me but it appears that other blogs are testing it and deciding it makes the grade. I will warn you that if you're using Firefox version 1.0.1 or any version of Netscape, don't bother trying to view it. Upgrade to the latest version of Firefox before clicking on this link. I want to expose people to the latest and greatest Google Maps mashups, but I don't want my links to crash browsers and make people angry with me. Now, on with the show...) --> Google Maps + NYC Subway system - This mashup takes ALL 400+ subway stations and plots it on Google Maps. There is Station Info popup markers and you can search and plot multiple addresses. There are only 2 zoom levels on this one because of how much data needs to be re-plotted each time you zoom in.
Map of Southern California venture capital investments (from socalTECH.com)