Don't even bother. I've tried everyone you named and more. While most of them are legit, there are two things which ruin them.
1) There are not enough of these "free" offers to warrant a prize. Anything that'll get you something good will require you to give out your credit card information to do an offer. If you are ok with that, just do a trainn site. Research it, they are a MUCH better alternative and you can start a trainn on CAG, if there isn't already one going.
2) You won't get any of your rewards for months. I specifically ordered a $10 Amazon.ca gift card from Rewards1 (filled out a form and everything). Then about 3 months later, I randomly got a $10 Amazon.com gift card from them.
So please don't bother wasting your time with these. The only one I do now is SwagBucks because that shit is legit. I always get my stuff on time with them, and it's the correct stuff.