I often get questions along the lines of "where can I get a free copy of [insert game title]?" I can't help you find free copies of games sold through retailers, but I can help you find places to download free games offered by independent developers.
Where to Download Free Full Version Games
Some independent developers have their games available online to for self-promotion. Some games are available to download free, others have to be played online.
 

Best Free Games : http://compsimgames.about.com/od/toppicks/tp/freesims.htm  
Links to Free Full Version Games: http://compsimgames.about.com/od/downloadfreegames/Download_Free_Simulation_Games.htm