Everyday minerals have generous samples which are free, and Lumiere charge $9 for their samples but it's free shipping. I've heard of a company that will sell you a sample kit for 1 penny but I'm not sure who that is.
Signature Minerals has a free sample kit you just pay for shipping. The Lumiere sample kit comes with a voucher for $5 off your first order so the $9 including shipping is not a bad deal. I've had samples and ordered from both of these companies but I think the Lumiere is my favorite.