are we talking about cutting and organizing before sewing? if so, i have 2 methods, depending on the size of the project. the first I use for long term storage, but some of my friends do them as a project organizer. Pizza Boxes! they stack nicely, are free (safeway's pizzas are heat wrapped in plastic so the box is completely clean inside, and my local pizzeria, Fillipi's, will sell their boxes from the stores...I always make sure to take one or two along to a class, that way someone will see them and order their pizza for lunch) and they hold a surprising amount. The other method i use for a project organizer is a large bath towel. the strips cling nicely and after cutting and placing in the order you're gonna use them, you can roll the entire thing and move to where you're working or just to keep the dust off if it's a few days before you get back to sewing.
or are you talking about keeping off the floor while sewing the sets together? this is a two part solution. I bought the large size mouse pads at the office supply store. this is approx 12 x 18 and gives a nice base for the sewing machine that quiets the sound and is soft enough that i can sew a big coat button thru it, on the bottom side. then, when i am sewing on something long and floppy, i reach under and hook a plastic grocery bag onto the button...everything coming off the machine bed falls into the bag and stays clean and untangled. I use the same thing all the time for my serger, where it catches all trimmings and clippings. (and of course, when you finish the first set of strips, you can just lay them back on the towel again!)