I just ordered tarps, from Walmart.com. It was the Foremost tarp 5'x7' for $1.99 plus shipping. I ordered 7 and it came to around $24 with the shipping. I ordered this size and weight because it seemed big enough that I could wrap up in it (I'm almost 6 feet tall) and still small enough to fit into our packs.
One of the most important things to have is shelter in an emergency. Tarps are great because they are water proof, cut the wind, and keep in heat. They are better to have than the emergency blankets. (We've heard those are junk. Thank you for the tip Kellen.)
I am also getting together the 2 tents we own for the family pack. I'll post a pick when the tarps come.