Here are 2 sites I use to get free samples.
BzzAgent - program where you get to experience products, services and more firsthand and then share your opinions about them with others (word-of-mouth) Campaigns are completely voluntary. The more you do the higher up the honeycomb you go and the earlier you get invited into trying things. One way to climb the honeycomb is to go to the Frogpond every month and review 3 websites.
VocalPoint - is a community of moms who love talking to others about their opinions and knowledge. You wil receive samples and coupons in your mailbox. Try them out and then give your feedback in short surveys and focus groups. The more you join in online, the more stuff you'll get in your mailbox.