Source: http://feeds.gawker.com/~r/lifehacker/full/~3/347771515/click-to-call-dials-calls-from-your-browser
Firefox only (Windows/Mac/Linux): The GrandCentral Click to Call Firefox extension calls phone numbers on web pages using your GrandCentral account with the click of your mouse. That means whenever a web page loads, the extension recognizes phone numbers on the page and turns them into clickable links. Clicking the number will call the phones you've connected with GrandCentral, and when you answer, GrandCentral connects you to the number you've clicked on. The extension is a little rough around the edges, but if you've been using the previously mentioned phone consolidation service (that's also been bought up by Google), it's a definite timesaver. Click to Call is free, works wherever Firefox does.
