Simple, inexpensive, green. These Rush Ottomans from Gaiam win on all counts. Made from renewable plant fibers, they come in a set of 3 (small, medium, and large) for $89. We think they'd work as a cheaper (but still eco-friendly) alternative to the high-end Cork Stool by Jasper Morrison.
We'd cluster these ottomans in a modern living room, maybe next to a Saarinen Womb Chair like the arrangement shown in this house tour from AT:SF.