Mini Map Sidebar
Mapping services are among the most useful sites on the Internet. Mini Map Sidebar allows you to open it as a Firefox sidebar, then drag and drop address names or links to it, and a map of them will open right in the sidebar. You have your choice of map services, including Google Maps, Yahoo Maps, and others. You can zoom in or out, get directions and do anything you can do on the mapping site itself.
Download Mini Map Sidebar
I use Select-n-Go by Cleeki:
http://www.cleeki.com/firefox.html
https://addons.mozilla.org/en-US/firefox/addon/7750
Here is a quote:
“Firefox’s enhanced alternative to IE8 Accelerator (Activities). Select any text on your screen and you can preview search results immediately in the same page. Support Google (text, image …), YouTube, Maps, Amazon, etc. and you can manage/add your own channels.”
As you can see, this is a generic add-on including quite convenient gmap services, so that I don’t need to add tons of add-ons for each desired features.