Any internet marketer will tell you that sales depends on three things.

1. Traffic
2. Copy 
3. Conversion

Any direct marketer will tell you three slightly different things

1. Targeted Market
2. Offer
3. Conversion

In the end though, they are basically about the same thing

1. How many interested people can find out about your product.
2. What you tell them about it
3. How likely they are to buy it

A lot of people consider traffic rather than eyeballs.  And they only think about getting traffic to their sales site.  I prefer to look at some other methods as well. 

If you have a product that is an extension of an existing piece of software, there is often a website that acts as a marketplace for those extensions.  For instance, this blog is run using BlogEngine.NET, which supports extensions.  Some of my products are modules for an open-source platform called DotNetNuke.  SnowCovered is one marketplace site that I use.  They take 25%, they host the files, manage payments, and run a helpdesk.  And 25% is less than you would pay most affiliates too.

If you are selling via the freeware/shareware model, the Association of Shareware Professionals has an XML file standard called PAD which allows download sites to create their site catalogs.  If you process your payments via a service like RegNow, then many of them will list your product for the affiliate fees.  Others will do it even without being able to use affiliate links.  This also has the advantage of building links to your site.