There are several ways to get free used carpet, including by using a website such as Craigslist.org or Freecycle.org. It's also possible to get new carpet for free by contacting larger carpet dealers.
Craigslist.org is a good source for free used carpet, and it's possible to find free new carpet, too. To use Craigslist.org, choose your location, and then the For Sale section. For Sale includes a category with the label Free Stuff, where its possible to search for carpet by keyword.
Freecycle.org works similarly, but all of the items on the website are free, and the website is free to use. To find free used carpet, type in a location, and then search the listings. In addition to searching the listings on Freecycle.org, it is also possible to post an ad on the site for a free used carpet. This way, those who want to give free carpet can make an offer.
It is also possible to find free carpet from large carpet dealers. Often, these dealers have large pieces of carpet remnants, which are new materials, that they are willing to give to those who ask. These remnants come from homeowners who have new carpet installation done and are left with pieces of varying sizes.