This topic is RIGHT up my alley. Here are a few pics of things I've repurposed to suite my needs. Now that I've got my own shop, the things I've built have really helped, since it's a small space and I'm a bit of a storage junky. Anyway, here are the pics with a little explanation. Click to enlarge the photos.
This is a small work surface I use when I need a surface more solid than my work bench. It's small, heavy and pretty solid so it's good to bang on, when necessary. The steel pieces were surplus yard finds and I paid for their scrap weight. I had the lumber, stain, etc. I probably have $25 into it.
This wheel rack I made from scrap leftover from shortening my pallet racking. Previously I had a wooden wheel rack, which was too small. I had to purchase the casters, some steel for the uprights, and some paint. Probably around a hundred to build, in total... maybe a few bucks more.
This is a score. I bought the box, filthy, for $25 bucks. The wood for the top I bought from a surplus place. Now I've got plenty of storage for consumables, bit's, etc. for the items that are near this, in the shop.
These racks usually go for BIG bucks but I found this for $125. Of course, I then paid for sand blasting and paint but I'm in for less than $250 for an item that costs north of 1K. It's really helped keep stuff off the floor too.
I've got some more that I could post up if time permits.