The Scorn Earth (Su) class feature of the Elocater prestige class (Expanded Psionics Handbook; pages 142-144) allows one to float, hover, walk, run, and fight normally... one foot above the ground (flat surface part of solid or liquid). It also allows one to move at a speed of 10' per round at elevations higher than that. There does not appear to be any upper limit on height, nor limit on duration. There is a penalty to combat when so elevated, however.
Other than the speed and the combat penalty, this is possibly superior to Air Walk in other respects. One might want to consider faster methods of elevation, and then sauntering around with this ability once you get up there.
Great for those floating meditating mystic old being mentor types, or wuxia stand-on-a-branch warriors, or impressively stand in mid air to look down on others characters.