Not much talk of free trials here, but if you search the shopping forum for "dvd rental" or some variety on that you should come up with some of our old online DVD rental threads.
http://urentdvds.com/rental.php?page=join - 15 days
https://www.wantedlist.com/SignupPlan.aspx - 10 days
http://www.pacificflix.com/signup.php - 3 weeks
https://www.bushdvd.com/join-freetrial.asp - 14 days
You've also got XRentDVD and SugarDVD where you can sign up for a free account but I'm not sure if that gives off a free trial. One more big dog is Adult DVDEmpire.

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