There are a couple diaper studies open right now, one is though Arquest and the other is through Nieto Research. I couldn't find a website for Neito Research but here is the website for Arquest. Although I couldn't find a website for Nieto Research, I have participated in one of their Diaper Studies before and was sent over 2 dozen diapers. I just had to fill out a form about each diaper package and what I liked or disliked, how they fit, etc.
Arquest need Boys and Girls who wear Size 4 diapers. If you are chosen you will be sent a pack of diapers, then you will be asks a couple questions about them. When you have completed the study they will mail you a $10 check for your participation. They tend to alternate the size of the diapers for the studies monthly. So even if you are not sure what studies they may be conducting you can call them and ask. They mail tell you to call back a month or two later depending on what size diaper your baby/toddler wears.
For boys use Ext. 634
For Girls use Ext. 646
You can call Nieto Research at a toll free number, if you don't get a live person then you can leave a voicemail recording stating that you would like to participate in a diaper study and leave your phone number so they can call you back. You can also send them an email at NietoResearchInc@aol.com or Nietoresearch@yahoo.com (Priority is given to those who email.). Tell them you would like to participate in a diaper study. They’ll need your name, phone number and child’s weight and diaper size. Nieto Research also has Feminine Care Product Studies as well. I just got a call today from them to update my info in their system, they said they had a study available but I didn't qualify since I didn't use that type of product regularly - "only when I can't afford my regular product", the lady laughed and agreed with me. Every time someone calls from Nieto they are always very nice.
If anyone gets in let me know, I would like you to add your experiences! Or if you have past experiences please share them with others by posting it here. Good Luck!