There are several ways to monetize domains on the Internet.
One likely everyone will know who is selling them, but there are other ways to earn good money with domains on the Internet, especially if the have the "catch dust."

One of the most widely used techniques in the Internet is the Domain Parking.  In what is the parking domains?
In fact is we are the owner of the domain (eg.: Www.text of exemplo.com) and put the same area parked.
Why and how this makes our portfolio? Simple.

There are many companies on the Internet for Domain Parking, we can put our domains for sale or simply parked.
When a domain is parked in a company of this kind, will run an advertisement, with which we will make money on every click made there.
Basically all that area that visitors click on advertisements or text incorporated, will be making our area.

Google also has an Adwords system to put parks in areas where the customer can return the same way the project.
Thus it avoids areas and annuities paid to "catch dust," when in reality could be paying good money.
Some holds some areas and parks can monetize them in 1000/1500 dollars a month only to advertisements.

There are also those who intentionally buy domain parked for putting money and yield.
This technique is advised, however, will take the names and potential business people. It is called the law of the market.