Viral Marketing is free, word-of-mouth advertising. It’s important to provide an incentive that encourages others to spread the word about your product, quickly and inexpensively with little effort on your part. This creates potentially exponential growth in the message's visibility and effect.
Hotmail is an example of successful viral marketing. The company started offering free e-mail accounts, with a link back to Hot Mail at the end of every e-mail message sent by one of its customers. That spread the word about the service like a virus, with every customer a virtual "carrier" of the message.

Benefits of Viral Marketing:

• Free advertising
• Short term gains — immediate visitors.
• Long terms gains — attract visitors for years to come.
• Exponential growth — reach a large audience with minimal effort.
• Automate your marketing methods - simply set up your campaign and reap the rewards.
• Inexpensive set-up — it requires very little time.
• Viral marketing tools are easy to develop (i.e. create an e-book without knowing how to write).
• Establish a solid reputation quickly.
• Easily combined with other marketing methods (i.e. include as an incentive with other products).
• Increase targeted traffic to your website quickly and easily.

These viral marketing strategies will help enhance your web presence, by rapidly increasing web traffic, gaining more links and establishing your reputation as an expert in your field.