The trick is knowing where to advertise for little or no money. Over the last 8 years I have mastered the art of seeking out little known nooks and crannies that provide excellent exposure for free.
One such source is the blog. A blog is an online diary. It is incredibly simple to update and maintain. You don't need a web host so there is no start up costs. You can pick up a blog for free by doing a search on Google for blogs. Once you have your blog start writing on it everyday. Pick topics specific to the product you are trying to market and write. Write everyday.
To gain additional free traffic to your blog visit a pinging service like Pingoat. These services will submit your blog to hundreds of feeds. If you are diligent at writing and pinging your blog will see traffic.
Get your blog listed in blog directories. Start submitting to as many blog directories as you can find. Again a quick search at Google will get you a significant list of directories to work with. The more directories you are listed in the more traffic you will receive if you write quality information on your blog.
Blog on other sites. Search for blogs relevant to your topic. Submit comments to those blogs. Be sure your comments are valid not just junk to get your name on the blog. Nobody wants to read junk. The more valid your comments the more valid the traffic you will receive from your efforts.
