Here are some links to free games....most are MMoRPgs and betas so your "free time" won't last forever, but I find it nice to explore new worlds.
http://www.gamespot.com/misc/betacenter/
This one is a page for current and future betas
http://www.planeshift.it/
A MMoRPG that will be free..still in early workings
http://www.terraworld.tk/
Another Free MMoRPG in the works
http://www.freeworldonline.com/
Yet another
http://www.ogaming.com/content/main-betalist.php
Another beta list
http://www.astonia.com/
This one you can DL and play free for 28 days
There are other "open betas" that you can find on the 2 beta lists above.
Below are games that you can DL and try for free for a certain time...they are established and usually (ie 99% of the time) require a CC number to sign up.
http://www.anarchy-online.com/
I recommend this one, even if just to try
http://www.shadowbane.com/freetrial.html
Havent tried this one, so I have nothing to say about it
http://microsoftgamesinsider.com/AC2/freetrial.htm
This one is pretty fun, the weapon animations (ie the acid blades, etc) are very nice to look at
There are others but I'm tired and need sleep...gl to you and your gaming.