Controller is a general aviation trade publication that serves the needs of buyers and sellers of single and twin-engine piston aircrafts. What you can find here is aircrafts for sale, for lease, for fractional ownership, Aircraft Dealers and others.
The homepage has a nice design where you can choose for an Aircraft from different categories and then shows you all the information about it with many pictures and sometimes with videos. You can add an aircraft to an interest cart, once you do that and only if you are already signed, you can have the Aircraft in your member account. Obviously it is not a simple click to buy an aircraft so when you are interested in one the seller will contact you to close the deal and how to deliver the product. The registration is free.