I'm interested in figuring out statistics as well and I would love if someone could share any resources they use. The best tool I've found is LinkedIn search queries. It's pretty general but it gives you an idea.
Some other sites I use when deciding some technical requirements:
http://netmarketshare.com
http://caniuse.com
http://www.tiobe.com/tiobe_index
http://www.statista.com/
you could find almost any kind of statistics for market research, with their paid account you can get even more.