I have recently began experimenting with various survey websites.  During one month, I received $25, a free CoverGirl mascara, and more points that I have not yet redeemed. Keep in mind, I did not spend excessive time on these surveys.  I merely was experimenting with the different websites in my spare time to see which ones seemed legitimate.

Once you get the hang of it, the demographic and starter questions on the surveys are quick and you can speed right through them.  Be careful though - if you go too quick, they may think you aren't putting thought into the answers and disqualify your survey so you do not earn points.

Update, August 31 2011: I wrote this in June and I have not completed any surveys in the meantime since I have had a newborn to devote time to while running my blog.  I am getting back into the surveys and am excited to start getting the checks and free products in the mail again!

Toluna
60,000 points - $20 check (minimum payout)
My earnings for the month: 75,000 points

I started taking surveys at the beginning of May and by the end of May, I earned enough points to cash in for a $20 check.  Many surveys are 1,800-3000 points and state that they should take anywhere from 15-30 minutes.  I requested my check at the beginning of June and received it in about 2 weeks or less.


MySurvey
1100 points - $10 gift card of your choice or other reward 
My earnings for the month: 325 points, CoverGirl Mascara to review

Surveys that I participated in vary from 5-150 points.  I did not really take too many of the surveys on this website, however this is where I was randomly sent a CoverGirl mascara for being part of the 20-25 year old female demographic.  A week after being sent the mascara, I was emailed that there was a survey on their website to complete.  The survey took less than 5 minutes to complete.  My survey has many different rewards you can cash your points out for.  You can request $10 gift cards or paypal cash for 1100 points.  The other awards seem to be similar in value for the amount of points required.


Synovate
5000 points - $5 check (minimum payout)
My earnings for the month: 5450 points 

Again, much like MySurvey, I did not spend much time on surveys here.  I completed a few here and there but did not qualify for many.  Synovate is reputed as a good survey company and I have heard great things about them.  Just for registering, I earned 500 points, but then I completed surveys for approximately 250 points each.  I requested my check just a few days, so I have not yet received it.  It should come within a couple of weeks.


Opinion Outpost
50 points - $5 Amazon, or 200 points - $20 check 
My earnings for the month: 50 points

Another survey site that I did not spend much time on and have only completed a few surveys.  I completed a total of 4 surveys, probably taking me 15 minutes each.  So I guess that means I made $5 in an hour which is less than most states' minimum wage.  But I did those while I was pregnant and could not do a whole lot else to make money, so I will not complain!  I am waiting until I have enough points to get a check so I do not know how long a check will take to be mailed.  It says 4-8 weeks, however that is the same as Toluna said, and I received that check in less than 2 weeks after requesting it.  Opinion Outpost is also well reputable among survey takers that I have met.


Overall I am happy with each of these survey sites.  At this point, I cannot pick a favorite.  I hope to receive more products to review in the future, but money is great!  Toluna seems to send me the most surveys but it all depends on your demographic and interests.  




Some I have not tried yet but have heard great things about:
Global Test Market
Inbox Dollars
Valued Opinions
Vindale Research