These look quite nice. They are called CenterSkates and are basically human powered, hubless skates.
http://www.thedesignblog.org/entry/jump-on-centerskates-and-roll-over-the-future-roads/
There's also a video so you can judge for yourselves if they'd actually be practical!
http://www.youtube.com/watch?v=L69YcavnFOY