Supported entirely by banner advertising, a number of companies now offer free e-mail. It's great for travelers who don't want to lug laptops around, as well as for people looking for a personal account at work. You can check your e-mail from any computer with Internet access. In recent years, free services have cropped up like mushrooms. Yahoo! Mail, Microsoft Hotmail, NetAddress, MailCity, and ApexMail are just a few. Also, American Express, CNN, and the Discovery Channel now offer free e-mail.