If you want furniture that does double duty, choose sofas, love seats, chairs and even ottomans that convert to beds. Converting the furniture usually involves removing the top cushions and pulling out a folding mattress and frame. You'll need to have enough space in the room to unfold the bed, and to make up the bed with sheets, blankets and pillows after you've unfolded it. Choose an armchair or love seat for a small bed for one person. If you have more room you can opt for a sofa that makes up into a full- or queen-size bed.
Beds that inflate with an electric or hand-operated air pump are easy to store and can provide a comfortable place to rest. Inflatable beds are up to a foot thick and are available as full- and queen-size mattresses. The beds need to be deflated for storage, though they can be propped against a wall to get them out of the way for a few days. They aren't as convenient as Murphy beds or convertible furniture, but they're very inexpensive and portable. You can carry them with you for a trip in a container the size of a small suitcase.
You can also find chests that open to fold-out mattresses or futons. The mattresses or futons roll out onto the floor. These take up more room than an inflatable bed, but they're still easy to move around.
If you're trying to put a bed in a really tight space, consider a loft bed. A loft bed rests on a platform near the ceiling and is accessed via a ladder. Loft beds have the advantage of not occupying floor space. If you leave the bed made, you can keep it mostly out of sight of visitors. But when you use the bed, you'll have limited head room and need to use the ladder. Loft beds aren't a safe option for children or anyone who has a tendency to sleepwalk.
A trundle bed is another space-saving option. A traditional trundle slides under another bed, but you can also find trundle beds that slide out of sight beneath sofas when the beds are not in use.