I have been absolutely mesmerized by Andy Goldsworthy ever since I saw the documentary.
Also, Theo Jansen. See here:
http://www.google.com/search?q=kinetic+art&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a#q=kinetic+sculpture+theo+jansen&hl=en&client=firefox-a&hs=YCT&rls=org.mozilla:en-US:official&prmd=ivnso&source=univ&tbs=vid:1&tbo=u&sa=X&ei=P-drTaLVGImctweO96nmAg&sqi=2&ved=0CDkQqwQ&bav=on.1,or.&fp=ed95a43a1d6a1527
Both are just brilliant, and on very different spectrum.