There are many market research companies out there who really do give you rewards for your time, however, you should read terms & conditions so you know exactly what they expect and what you're going to have to invest time-wise before getting anything out of it.
While you can just do a general google search and see what you find it's probably easier to go to the websites of market research companies directly (there are thousands, of course) -
American Consumer Opinion, Ciao, ipoints, testandvote, and others actually do offer money in return.
sometimes the terms and conditions mean you have to qualify for a certain number of surveys first or some of them have such lengthy surveys that it's really not worth it, but it can be fun and, after all, you are shaping future consumer products (might as well have a little impact on what we have to put up with!)
Many sites also don't offer straight money, but vouchers instead. These can be very good depending on the company and what your needs are (e.g. shopping vouchers, amazon etc). Alternatively, a lot of sites have a point-earning programme which can work out depending on how much time etc you put in, but again, check everything out carefully before committing lots of time to sites that don't pay a lot in the end.
Finally, a lot of them obviously do regular prize draws etc amongst their members and they are all free to sign up to (the ones that charge you are most likely dubious) - so as long as you can put up with lots of emails and additional spam from associated companies, you're fine. (and there's nothing better than receiving the cheque in the post - even if it's not a lot, every little helps!)
Good luck!