I have a two wheeled cart that has been extremely useful and easy to maneuver. I prefer it over other carts that I have had. Mine is much like the one pictured in the attached link. I've had it for a very long time, and simply repaint it every once in a while help preserve it.

The 'easy to maneuver' part is the most important feature, as far as I'm concerned.

Here is a link that might be useful: Click here for information

Tiny, just to be clear.....I posted the picture of that cart simply to show you a style that works for me. I would think that such a simple design could be duplicated or improved upon.

See picture below of a 3 x 6 work bench I built for the garage. It has swivel casters at all corners. If I was going to use it for plants, I'd lose the OSB/carpeted top & replace it with a sheet of FRP. I'd build the top so the FRP sagged slightly toward a hole in the middle, so when you water & inevitably spill or collection saucers overflow, the excess water flows to the center hole & drips into a collection vessel you can empty at your leisure. It's even wired, so all I need to do is plug it in to have electricity at the 3 outlets (can't see them in the pic).

Alternately: I just bought a HDPE service cart from Harbor Freight for $120, similar to the one you'll see if you copy/paste this link to your browser:

http://www.amazon.com/Rubbermaid-Commercial-Heavy-Duty-500-Pound-Capacity/dp/B0007Y1SJQ/ref=pd_cp_hi_1

Al

This is what I ended up putting together. Two 4'x4' carts with 3" wheels, built of pressure-treated decking and doubled 2x4's. If I had to do it over again, I would have made the carts more like 3x3' with 4" wheels. Loaded, these things are heavy and don't move as easily as I'd like. Still, it's better than dragging the plants back and forth. My mother-in-law seems pleased.