should i really sign up?

Yes. There are memberships on some sites that are worth the time and emails to sign up for. This week I used some coupons for free items that I had received from some of these so called sites.

Kraft First Taste: http://www.kraftfirsttaste.com/ 
A month or two ago, I received a coupon for a container of free Philadelphia Cooking Cream. This time a free box of the new JELLO Temptations. I would check this account once a week. Sometimes you won't always get the free item but rather a coupon for it. They currently have a coupon for free Kraft shredded cheese with a touch of philly, I only got $1 off. Worth it!!

Vocalpoint: https://www.vocalpoint.com/registration/screener.aspx
Vocalpoint sends out emails with a lot of really good ideas in them and also gives you an update as to what samples to can ask for. I received my first coupon from Vocalpoint a week ago it was for a free pint of Breve coffee creamer.

Right@Home: http://www.rightathome.com/   
They send out monthly emails updating you on new deals and tips around the house. Yesterday I received a coupon for a free Glade spring collection product.

All in all my shopping trip yesterday was on the free side.