A colleague recently informed me that Workbench has released extensions for both Firefox and Chrome. In Chrome it puts a Workbench icon on the right side of the location bar when you’re logged into a Salesforce production or sandbox site. Clicking on the icon logs you into Workbench for that instance in one easy step. As a bonus, it uses your local ip address so that you can get around any issues you may encounter with restricted IP ranges on your profile (ie the error message; Invalid_grant: ip restricted or invalid login hours).
Installing the Chrome extension was a bit tricky because Chrome has changed to only allow extensions installed from the Web Store which doesn’t have this extension available (yet?). You can get around this by downloading the extension from the project site. Then in Chrome, go to Window >> Extensions and drag and drop the extension onto the page. This will allow you to install it manually. Reboot Chrome and you’re ready to go.