If you've got some extra time on your hands (from 10-55 minutes per survey), you can earn some extra cash just by taking surveys online. You might even get a free product test at some of these sites too!
Here are some of my favorite survey sites. I've listed them in categories based on how much you have to earn to cash out!
$5 cash out
Opinion Outpost - Sometimes I'll get plenty of surveys from this company and sometimes I'll go a week or so without any. BUT--I've gotten lots from them in the past, so, it's still one of my faves! This site will email you when you have new available surveys, so you don't have to visit the site every day! $5 Check or Amazon certificate code cash out
Lightspeed Panel - Good site with lots of surveys. This site will email you when you have new available surveys, so you don't have to visit the site every day! $5 Paypal or Amazon certificate code cash out
Ipsos I-say - Pretty fun surveys. Will email when you have new available surveys... $5 check
Clear Voice Surveys - I just joined this site, and I get at least one survey from them a day, if not more. I also just got a free paid product test for a great product too! This site will email you when you have new available surveys, so you don't have to visit the site every day, but you can find new surveys when you visit the site too. $10 Payoneer debit card or Amazon certificate code cash out
$20 cash out
Valued Opinions - This site pays pretty good for surveys, though they seem to go through spurts of sending lots of surveys and sending few surveys. $20 Visa gift card, Amazon gift certificate and many more options
Toluna/Greenfield Online - Toluna and Greenfield recently merged to create this new site. This site is okay, but sometimes you will spend a few minutes on a survey and then find out that you don't qualify. So...I don't take surveys with this site unless they are short or they are worth a lot of money and make it worth my time. Will email with new surveys. $20 Paypal or check (these checks take a LONG time to arrive)
$25 cash out
Surveyhead - This site has SEVERAL surveys daily, but they don't usually email you about them, so you have to visit the site every time you want to try to qualify for a survey. The cash out amount is high, but they have so many surveys that it shouldn't take you too long to reach it!
$25 Paypal, Amazon gift certificate code, and many others
$30 cash out
Inbox Dollars - This site pays you for reading emails and responding to offers. You get paid for each email you read (sent to your inbox), regardless of whether or not you sign up for the offer. There are plenty of free and other great offers, so, even though it takes a while for this to add up, you don't really notice because it's so easy! $30 check
Send Earnings - This site is almost exactly like Inbox Dollars. In fact, I think it must be the same company :) $30 check