We already knew that Ikea Expedit bookshelves could be turned into a bed with tons of storage, but you can also use one as an attractive bench.
As far as IKEA hacks go, this one is about as simple as it gets. You'll basically set the unit down on its side, and put some pillows or cushions on top. If you want to decorate the backs of the shelves, IKEA Hackers suggests covering squares of cardboard with wrapping paper, and attaching them to the back. However, if your home is short on space, I could see sticking some fabric storage cubes in the compartments instead.
For more photos of the project, check out the source link. The guide calls for a Lack bookshelf, which is no longer available for sale, but an Expedit should work just as well.
IKEA Expedit Bookshelf to Bench [IKEA Hackers]