As far as I know FortuneJack will require you a little deposit before giving you free spin. I am not sure though. I remember last time I checked it and saw this kind of requirement.
For the 25 free spins there's no required deposit but it's only for new users. This is always shown on their homepage if you haven't checked their site.
mbitcasino offers no deposit free spins too but I don't recommend making a deposit because there are unsolved scam accusations against them.