Luckily, I spotted Michaels semi-annual storage sale in their weekly add. There were no prices listed, so I thought I'd pop in to see what the options/costs would be (as if I ever need an excuse to visit Michaels!).
They had an amazing selection of stackable storage. Basically a square pod with all number of storage options; some with shelves, or drawers, or containers. I calculated that by stacking 2 together (they come with special plugs especially for stacking) I would have a counter top height of 29" - the perfect height for a desk. One style was on clearance for $15 so I bought three of those, and one that was originally $35, but $17.50 with my 50% coupon. All in all it cost $62 for the base.
They were super easy to put together (if I can do it, anyone can!). The three holes are actually a file folder, and the drawer with the long opening is for ribbon, but will be perfect for posting letters in. I have it all planned out. Organisation here we come!!