PPC (Pay Per Click) is a great method to bring high quality traffic to your site.
Because of the High competition, the bids for PPC on the main search engines (Google, Yahoo and  Bing) are extremely high and on some cases Inexpedient.

One good alternative for PPC = PPV advertising.

PPV advertising – means that you pay every time your landing page is viewed. Although that  sounds like PPC it’s different because to view your landing page no one is clicking. Your landing  page is appearing in a pop-up or pop-under.

Pay–Par–View advertising allows advertisers to both bid on keywords or URLs and display  their ads in both situations. whenever a user searches a keyword or visit a URL that’s being bid on –  the corresponding ad will be shown to the user.

PPV traffic convert less then PPC traffic but the cost of this traffic is extremely low which make it Worthwhile and good alternative for any PPC program.

One of the coolest PPV network call DirectCPV On the link below you can watch video that explain more on PPV advertising and start your first PPV campaign:

==> Cool PPC Alternative <==

Remark:
PPV ads are displayed to users who have chosen to install ad-supported software. some peoples linking adware with spyware. Basically A software that shows advertisements on a computer is called an adware. If it is installed upon the consent of the user, the adware is counted as part of permission-based advertising. On the other hand, a spyware is an unwanted program that spies on the online activity of a user, monitoring information and transmitting it to an external entity.