Long before Mr. Murphy created a bed that folded into a closet, the most functional family furniture has been the most expandable: drop-leaf consoles that stretched out for large dinner parties, and stacking stools that could be used as individual tables. Along with the venerable nesting table set, these pieces often conceal their flexible nature behind stylish flourishes. The latest innovations make a virtue of their gee-whiz technology. Just take Inova's TableBed, a free-standing wall unit (available through Bedfellows in Studio City,  985-0500) that goes from dining to dreaming, or the self-inflating EZ Bed, which can be packed into its own rolling suitcase (www.frontgate.com). At their best, square-footage savers such as the Par 4 coffee table on F1 (an iroko wood frame and four sliding leaves, $1,498 from Design Within Reach) merge clean geometric forms to make a design statement that doesn't waste an ounce of space.