Everybody else in the universe probably knew about this already, but several people that I know didn't. I've always been worried about using Gmail because only the login was protected when using http://www.gmail.com. However, after searching the help I discovered that you can use https://www.gmail.com or https://mail.google.com. I wonder if the your IMs are encrypted when going through the web interface?
You should probably use https://gmail.google.com/gmail. This way you get the little icon when you bookmark the site in firefox.