I'm a member of multiple survey sites. I'll list my favorites below. This post contains affiliate/referral links. You are not charged anything extra for using my links (you shouldn't be charged anything at all, unless you are making a purchase through Amazon). I'll try to add to this as things change. I will list 4 to start with.
4. MintVine Not only surveys, there is also an offer wall. 1 point = 1 penny so it's easy to keep track of how much you've made. Cashout threshold is $10 and it's really easy to reach. They pay via PayPal.
3. iPoll- I like iPoll because they offer multiple options for cash out. The drawback is it takes exactly as long as they say it will for you to get your reward. This is typically 4-6 weeks. I've never had a problem redeeming a reward, and they are quick to answer tickets if you do have a problem. Filling out the profiles completely helps to ensure you get a good amount of surveys. Surveys range from short with small award ($1 for 10 minutes) to long or multi part with larger rewards. There are higher value surveys, but they go quickly. Try to do them as soon as you get the email telling you it's available if it is a larger dollar amount. They do have a PayPal option, but the cash out threshold is $50. They also offer $25 Amazon gift cards.
EDIT: iPoll has changed their payout structure. If you choose PayPal now (now with a $25 threshold) it's pretty much instant payout. I haven't tried any of the other methods since the change as I would rather have cash than gift cards!
2. Swagbucks- of course. Most people have heard of Swagbucks. There are many ways for you to earn sb and cash out. How much you will earn depends on how much time and energy you dedicate to earning.
1. SurveySavvy- This is the one I have made the most off of, by far. You can make $50 per opportunity if you are in the target demographic. They pay by check, and it seems to be pretty prompt from requesting a check to getting it in the mail. I tend to get the check within 2 weeks of requesting. There is software you can download to earn passively, which will also qualify you for more opportunities. You can earn more for having more devices connected. All in all, SurveySavvy is my favorite.
Surveys won't get you rich, but it is a good way to help you get a little extra. I like to use mine for holiday shopping or treats for our family that we wouldn't necessarily do otherwise. I'll do surveys during nap time or when my son is watching a movie. They're easy to do and the extra cash is nice. Hope that helps!