Nice compact hay bales make nice back stops.

Something else that makes nice targets, but takes a bit of work is cardboard. You cut strips at least 12 wide by about 3 1/2 to 4 feet long, then stack them. You start with a nice sturdy piece of plywood on the bottom, lots of cardboard strips all cut to the same size, then end with another piece of plywood. You hold it all together with 2 long pieces of all-thread on each end. Just need to collect all the big boxes you can lay your hands on. I like the large ones that appliance stores get their appliances in.

Now for foam, if I remember correctly we used to see that in surplus types of stores. Maybe Lowe's or Home Depot carries it too?

Boat dock foam is the only foam that will last for more tha a few hundred shots- Foam is not an ideal target. Poly foam is good, but arrow removal is pretty hard. You can buy a blob target that is made of melted down carpet padding for about 50 bucks and never wear it out if you'll shoot it with broadheads every day.
Compression layers are cheap to build and you can use cardboard or rubber layers. I have a link somewhere. I'll find it and post it here.

Thanks alot i'm trying to go on the cost effective side.The cardboard idea sounds good.I read in a old FFG that feed sacks stuffed with grocery bags will stop even the fastest arrows of course the didn't have the Mathews Z7

Any more ideas would be fine.

Plastic wrap like what they use to keep different things on pallets works great stuffed in a grain bag.
Go to Archery Talks and look up targets. They have some good ideas on there.

heres a thing i use.
do you have a hot tub dealer in your area,
he throws out the old hot tub covers.
ask him or her to save you a couple they make excelent back drops
or if you want saw -all thin into squares and bind them with shipping strapping.
i have 5 that i scatter out behingd my 3d targets depending on the range setup.

I made a target a few weeks back from old rags and clothes that needed to be cleaned out of the closet.  All I did was take a feed sack and stuff it tight with clothes and rags, making sure to cut off any buttons or zippers.  Tied the top of the bag off, and painted some dots on it.  I'm shooting a switchback @ 70lbs with a 420grain arrow and my arrows are only getting 5-6" of penetration.

I used to make my own targets.  I worked at aplace that had a lot of used shrink wrap.  I would just pack a few different size boxes and I was good to go.  Wghen the box wore out I just got a new box and reused the shrink wrap.  Made quite a few for fekloow hunters.  Almost with I still had access to that large amount.