Quick Maps is a Mozilla Firefox add-on that lets you search for locations inside the site you are currently browsing.
As opposed to manually opening Google Maps in another tab, you can highlight an address and Quick Maps will show the location in Google Maps through a pop-up. If you need, you can tell Quick Maps to open a new tab in Google Maps.
Using the add-on is easy and very helpful so you are not constantly opening new tabs for Google Maps and copy/pasting. The only issue currently is that Quick Maps adds a link to addresses in the United States, England, Germany, and Spain, but you can highlight an address and right click to manually search an address in other locations.
Quick Maps is a great add-on, giving you Google Maps on any site you're viewing.