A company called Musical Furnishings has developed a series of products including coffee tables, chests, and outdoor furniture that you can actually play music on. All you need is the included Marimba Mallets and songbook to help you get started.
The sound that this furniture gives off when played is actually fairly impressive. You can check out a movie of the furniture in action here.
Prices range from $300 to around $1300. Each piece is hand-made by the designer.