SampleSource

SampleSource is a simple sample opportunity that lets you try samples in exchange for a product review through their website. All you have to do is sign up and when samples are available, they contact you through email and you claim your sample box. A few weeks after you receive your samples they will email you again with a link to review your samples. While I have gotten some really great samples from SampleSource, the only downside is that they don't offer sample boxes very often. 
Samples are available in the United States and Canada.
TIP: Make sure you sign up for SampleSource with an email you check often, when they let you know when their samples are live they go fast, so you need to claim yours quickly.