Brand Power often have free samples which can be very helpful, you can subscribe to their site here for free:

Brand Power » Home Tester Club

From the page:
Our 'Home Tested' section is where our members register for new sample boxes, and answer a few survey questions once they have received the products to sample.

Hair Care Samples Available!!

To register, please let us know if have you EVER experienced any of the following hair conditions:
In order to register your interest in receiving this sample, please login first