Creative viral marketing is sometimes effective. You have probably seen some short video clips for example that at the end advertise the company. However for the most part these tend to be expensive. Other types of viral marketing ie sending out mass emails without the recipient opting in can get you into trouble - there is specific legistlation prohibiting it.

With the time you would use trying to viral marketing I would suggest you:

-write articles and submit them to directories
-post on forums like this one
-perhaps consider writing a blog

All of these would be more effective