Opinion Outpost is the best survey site I have found on the internet. Most survey sites give you invitations, which means you can never truly work whenever you want. Opinion Outpost doesn't do that. You can log in whenever and there are a number of surveys to fill out 98% of the time. Most of them pay pretty decently too, about 2 to 3 dollars per survey. You get paid in points, but you can trade them in for real cash via pay pal.
Here are some negative things about the site. It used to be 10 points, about one survey, to be able to cash out. Now the cash out limit is 100 points, about 10 surveys. Another thing I don't like about it, is they will boot you off a survey right in the middle of completion, with no reason given. You also have to fill out a questionnaire before each survey which is not paid. But if you're persistent and don't give up after one disqualification or unpaid questionnaire, you really can make about 10 dollars a day on it.
Another cool thing about it I forgot to mention, is if you do get booted off a survey, you get a chance to win some points by playing some reward games that they offer. I've done these a couple times and have won 5 to 10 dollars for literally doing nothing. Not bad. Now is this site still worth your time? Probably not, but it is definitely the best survey site that you will find online.