Use pallets to make planters or plant pots.

Step 1: Basic Frame

The worst bit is first. Take apart a few pallets and de-nail them. I used a Pallet Reclamation Bar.

Cut 4 legs the same length.
Cut 8 side bars to the length you'd like the width of your planter.

Step 2: Frame Assembly 1

Build two matching sides as pictured.
The lower side piece shouldn't touch the ground to avoid water, I left around an inch free.

Step 3: Frame Assembly 2

Use the 4 remaining side pieces to construct a very simple cube. I used screws for this whole process.

Step 4: Side Panels

Cut side panls from pallet boards. You'll need a load if you're building a big planter like this.

Since I was using lots of different pallets here, I attached the boards in a random order to give it that rustic look.

I used nails for the sides as they look nicer and aren't load bearing. Try and re-use the nails you took out of the pallets if they're straight enough

Step 5: Top

When you're done with the siding, cut four more pieces for the top as shown.
Cut these pieces at 45 degrees to make a nice looking top.

Step 6: Done

These planters would rot pretty quickly if I put soil in them (not to mention I didn't build a bottom).

Instead, I used an old bin to put the plant in. Hopefully whatever you plant will hide a bit of the bin or barrel.

The other pictures show another planter I build from half a leaky water butt.