I got pillows, an outdoor rug, and my cube ottomans covered so the deck is looking a lot more inviting.
The cubes were $10 a piece at a thrift store. After covering them in fabric (it took 4 yards) I sprayed them with a fabric protector from Jo-Ann's to make them "outdoor proof." To attach the fabric I simply stapled it on the underneath and on the inside (the tops come off so I could easily access the inside).
This has quickly become my favorite place to relax with a book!