Here are the ones I belong to and think are worthwhile.
all of these coupons are from Kraft, either from their First Taste site or by "liking" Kraft products on Facebook. You don't have to do anything at First Taste, just join, and then when Kraft has products they want to promote, they send out coupons or samples. You do have to check your account occasionally and accept any new offers to get the coupons.
Vocalpoint is another site that promotes new products. Just sign up and check out the Try and Tells to get samples and coupons.
In yesterday's mail, I got this cute cardboard purse from VocalPoint.
It contained 3 of the new very thin Pampers as well as some high value coupons.
I just started Swagbucks about a month ago and plan on earning Amazon certificates. I mostly use it as a search engine, I do a few searches several times a day, hoping to win a few bucks, I also do the Daily Poll everyday for 1 swagbuck.
I have belonged to MyPoints.com for about 10 years. My husband also has an account. Most of our points come just from clicking on the links in the emails they send. We also get points from some online purchases including Ebay and for printing and using coupons at our local stores. I spend maybe 1 or 2 minutes on some days with Mypoints and earn a $25 gift card every 8 months or so.
If you have a blog and like to host giveaways, I recommend MyBlogSpark.com. I have hosted for them several times, they usually send me some sort of gift pack to try and then a giftpack or gift card for a reader that comments.
None of these programs will replace earnings from a fulltime job but most of them are fun and do offer rewards. I would be interested in hearing of any other reward programs with good reputations too.