I do Valued Opinions and One Poll for fun. I've always been the kind of weirdo who enjoys doing surveys, and occasionally you might get sent a free sample of a product to test, and every so often you get a voucher for Amazon (or can choose from others such as Tesco etc) or with One Poll you get a certain amount put into your paypal account. You can't live off it as a sole income, but it's an alright way to get a (small) bit of free pocket money.
ooh thanks for the heads up on one-poll, hadn't heard of this site
there is also Saros which is legit, paid market research (my sis did some stuff with them). Instead of filling online surveys though, mainly they expect you to attend real life focus groups, for which you can get paid anything from £30 to £100 for attending. The two bad news about Saros is mostly the groups are in London, and there is usually a limit on how many you can attend, a lot of the companies won't let you attend if you have attended any other focus group meeting in the past six months for example.
https://www.sarosresearch.com/