I got this fabric from Hobby Lobby - regularly $40 a yard but with a 40% off coupon it was $24. I plan to make another one of these so the total fabric I needed for 2 cubes was 4 yards or $96. Obviously you could do this for a lot less with a different/cheaper fabric. Most of the poufs I have seen for sale range in price from $200 to $250 so I felt ok about each of mine being around $50. I wanted my poufs to be 18"x18"x18" so I cut out 6 squares of fabric 21"x 21" for each pouf. Then simply sew all your squares together to create a cube, leaving one seam open for stuffing. I wanted the seams on the edges to "stick out" a little bit so rather than sewing the "right sides" of the fabric together to create a basic edge, I turned each of the fabric edges over about an inch then sewed those edges together about a half an inch in (with the two wrong sides of the fabric together). Don't know if that makes sense - but it's the best explanation I can give!
Once it is stuffed, sew your last seam up by hand and ENJOY! This is the tv area my kids primarily use and so I haven't ever wanted a "hard edged" coffee table down here - it just seems like it would be a bit of a hazard with three boys jumping around. This is a great solution for me, a nice soft spot to put my feet up on when I am sitting on the couch and it easily moves out of the way when I'm not using it.
Now I'm off to finish the other one!