We have used card board, used carpet pieces and anything we can find for weed control...they all seem to work pretty good.

Don't use carpet! It can be a complete nightmare. There have been a number of posts on gardenweb lamenting the use of carpet for weed block. When weeds or grass grow through it (and they will unless you weed regularly), you have to take the entire thing, including the vegetation, up all at once. You'd be better off with nothing than with carpet.

I have had good luck with cardboard. It lasts long enough to completely kill the vegetation underneath which is what you want.

We had no trouble with the carpet...none what so ever.

Below are a couple of links to some example Gardenweb posts by people who have tried it and found it to be a problem. BTW, according to some of the posts on here, there are serious chemical and biological DANGERS in using old carpet in vegetable gardens!

http://forums.gardenweb.com/forums/load/flgard/msg0723114211638.html

http://forums.gardenweb.com/forums/load/weeds/msg091032144755.html

Here is a link that might be useful: Carpet Mulch Problems