Needed materials for this project:
* guts
* the ability to talk to strangers
* the knowledge that you're doing something pretty neat

Okay, now I'll tell you about the carpet.  The answer is one particular big chain hardware store.  This is how it happened: my mom and I went there and asked if they had carpet sample books in the back that they were going to get rid of, that they wouldn't mind donating to a young artist who wants to make a dollhouse.
And you know what?  They have little carpet sample squares hidden everywhere in the flooring section ripe for the taking! And they have thin plastic wood-looking floor square samples.  They even have samples that look like marble.  They even have actual thick wood floor samples.  The only thing they don't have samples of is tile.

Here's an Example McPicture!

Be sure to ask first, when you go sampling, so they know you're not up to anything shifty.  And, personally, I try to never empty out a full sample box.

Here's what you're looking for when you look for carpet.  You're looking for a short-fibered carpet square that fits easily together with other squares and won't unravel when they're cut.  You might need to trim the sides a little to get them to fit together.

 Home improvement stores are fantastic resources, and they sometimes have wood scraps that they want to get rid of.  They might laugh at you a little, but you probably just made their day by asking the weirdest question ever.  I haven't come across anyone who's been anything less than helpful!

Happy arting!