MTurk is the only serious contender mentioned here. Everything else is a joke and it's even worse if you don't live in US. I hear content writers make decent cash but I'm not that good with words to try it.
I agree about Mturk really being the only thing worth the time and effort but even with Mturk, some of the requestors are jokes. Some try to get away with only paying a penny or so to do work that takes you 10-15 minutes to complete or is near impossible to finish in the time they give you. Then there are the ones who reject arbitrarily just to get out of paying.
There are other crowdsourcing sites including cloudcrowd and clickworker. I've tried Cloudcrowd which requires a facebook account. didn't really care for it. There's another called Clickworker that claims to pay nine bucks an hour but I also tried that and the work there is scarce.
There's also megatypers.com and that's literally just typing captchas. From my experience, there isn't a whole lot of work there either and you have to be invited to join. Humanatic basically has you listen to phone calls and then categorize them.
In the Google Play store there's an app called Locket which pays you a penny each time you unlock your phone. It's only available for Android users only though.
I know this was sort of long winded but my point is, you're not going to get rich off any of these sites. In order to make any decent amount of pocket change, you'd have to invest time in more than one.