1. Folding Crates from the Container Store collapse and come with optional casters.
2. The Umbra Crunch Can is easily scrunched down to a few inches but when it's open it can store a ton of toys, laundry, or stuffed animals. Handles make it portable.
3. We've mentioned the Reisenthel Market Basket before. The kids version has a drawstring to keep things contained and the basket collapses to save space when not in use.
4. The Komplement basket from IKEA can adapt to many different areas of the home and folds flat.
5. Target's itso Large fabric bins will fit your IKEA Expedit; plus, they're sturdy and fold flat.
Small Cool Lessons: Discovering Small Space Design Ideas That Really Work
Marisa and Peter's Playfully Eclectic Home
Good Food to Share 
The Big Book of Small, Cool Spaces 
Apartment Therapy Presents 
The Eight-Step Home Cure 
Z2 iPod Dock and Wi...
How to Make Easy 3-Ingredient Energy Bars at Home
How to Make Fresh Pasta Dough in the Food Processor
We have several of these around the office and the handles make them so easy to move: http://www.staples.com/Staples-Expanding-Folding-Crate-on-Wheels/product_440122
I would like to nominate 31 Gifts! They have amazing storage and organizational products that can be used at home, work, car, beach, dorm room and so much more. And yes, they are all collapsible! They come in lots of different patterns and best of all, they are very reasonably priced. The large utility tote is $30.00. Check them out and maybe add them to your list. www.mythirtyone.com/samharris
I appreciate that you'd want to plug your business, sarasam, but I actually lost all interest in viewing anything from your company once it became apparent that I'd have to "flip" through each of the 50 pages in the online catalog individually to find anything and be accosted with sales pitches to become a consultant with each turn. Gag.
that container store folding crate is exactly the same as the one i just picked up at ikea....for $5. no casters, though.