I had heard about China's weather modification efforts before, but this article has more detail than I had seen. Beijing is spending significant resources on this, especially as they get ready to rid the Olympics in August of unwanted rain. The problem, of course, is that it is very hard to prove it really works. Still, a fascinating effort.
"...the state-run news agency Xinhua claims that between 1999 and 2007, the office rendered 470,000 square kilometers of land hail-free and created more than 250 billion tons of rain--an amount sufficient to fill the Yellow River, China's second largest, four times over."
My wife and I are headed to Beijing in August - I look forward to seeing if they really manage to stop the rain.