[anthony_franco]

I haven't done it myself (only been doing research) but WordPress plugins might fit the bill. Mostly due to the fact that the WordPress plugin directory does some of the marketing for you. Also many WordPress owners are willing to pay money to improve their websites.

[stevekemp]

The problem with the wordpress plugin directory is similar to the Android/Apple appstores - getting discovered is hard.

There is very definitely a lot of fake reviews, and gaming, involved in most of the popular plugins. The fact that you mostly have to have a SVN repository hosted on the wordpress servers also means your source cannot be kept private - admirable, but quickly leads to cloning of novel and unique plugins.