This is one of my favorite features in Internet Explorer 8.
Click on Alt on the keyboard so the Menu shows up and click on File and New Session.
For a keyboard junky you can use Alt+F followed by “i” followed by Enter.
Now you can log into multiple Hotmail, Google, Gmail, Twitter, Yahoo or whatever account simultaneously. If it does not work you might need to deselect “Remember Me” option for the login as it might use a persistent cookie that is shared across sessions.
If you want to create a shortcut for this you can use iexplore.exe with the -nomerge parameter. "C:\Program Files\Internet Explorer\iexplore.exe" -nomerge