Products sold online can be digital products or physical products. Physical products can be books, CDs and many other physical items. Digital products on the other hand are mp3 files, E-books, software and other downloadable files or online services.

Developing digital products shouldn't cost much. You only need a software to compile your product into a downloadable e-book. But first you need to gather the information to be stored in the e-book. It shouldn't be just any kind of information, it should be valuable and worth paying for. Here is a very good software you can use to create your e-books and sell them, E-book Pro.

How do you get the information?

Something you know and you know will benefit others, something you are good at, a hobby or something you have learned from your profession or just life experience. 

Write all you know about the subject. For example if you pets and you know how to train them, you can write a book on how to train pets and include information on pet care and their habits, you'll be surprised how people will love it.

Other ideas I don't hear people talking about much is connecting buyers and sellers. Here, you don't need to produce any product of your own, you just put up a site and try to connect people trying to sell items with people looking for that item to buy.

You do so by setting up a website, attracting sellers and make them place their ads, and then attract buyers of the items. With time, you can charge a fee for placing ads from the sellers.

Though, you have to target a single market. People that want to sell their kitties with people that want to by kitties, people that want to sell their sport cars with people looking for used sport cars. Targeting matters. Though these are just examples, put you can use this idea and the tool I'll mention to discover a fresh market and sell to them.   

You can use the Overture tool to find lucrative markets. This is how you should use the tool;

Type in any phrase relating to your field of interests and click the go button. The result will display number of monthly searches on the phrase and related phrases. If the searches are in a few thousands, then the market is worth giving a shot.

You should also make some searches on Google, Yahoo! and any other big search engines to have an idea of how competitive your keywords are. Try and use the keywords with most searches and less competing pages to target your visitors.