With the Joomla list you can get into some joomla forums and find the hot topics, key phrases , then goto Survey monkey and create a free survey for them to fill out to shape your product ideas. The 18 K. listsounds like it's not quite as specific as this joomla list, so you might do a free survey where you're just trying to narrow down a more specific market.

This would be the best way to get started creating products for your markets by simply asking them what they want