In my previous posts I have lead you through how to make an AppleScript that can use to open a particular website URL in a particular browser. You can drag these Apple scripts to your dock to instantly access any URL from your dock. Obviously the next step is you will want to give these AppleScripts their own icon so that you can identify them from the dock easily. This is really easy to do in OS X.
One click on this icon in my dock and Google calendar opens in Firefox from my Dubbo.org G-mail account. This script has chosen the browser and the website and the account that I want to be logged into when I visit the website. This article below describes how to write the script to open a URL in a specified browser. To auto-login as a user see here. To customise the icon see here.