I got a Keurig B50 from Costco two weeks ago, and set it up in my kitchen. Between the 18-packs that came with that and some 5-packs and 25-packs I ordered from Keurig, I had a storage mess on my hands; you can't get into the 18-packs when they're stacked, and I didn't have enough counter space to leave them all out.
I went shopping at the big-box mall, and found the Sterilite #2003 Small Countertop Drawer unit at Target. Each unit's about 7" high, 7" wide and 8" deep and they stack. 3 drawers per unit are just barely deep enough to hold 9 K-cups each when arranged just so; the Tully's cups bulge on top and I have to be careful with opening and closing their drawers! I've filled each drawer with a different variety or an assortment of singles. The remaining 5-packs will sit nicely on top. I have the 25-packs and a bin of loose K-cups from the 18-packs under a counter on the other side of the kitchen, and I'll refill the drawers from there when they get empty. Now I can see what I've got when I'm getting going in the morning.
I'd love to hear from other folks about what they're using!