I made these this spring, but I thought I'd share to give others some inspiration. The linen "Far, Far Away" collection makes great outdoor cushions. I wouldn't leave them anywhere they could get wet. My porch is covered so it works out. Here's a close up of the fabric:
I put zippers on the sides so I could take the covers off to wash them. It was kind of hard finding 27 inch zippers to match but I managed.