Planet13 - 4:01 pm on Jul 5, 2013 (gmt 0)
Well, the easiest way I know of is to look in google webmaster tools since it does show average rank position in there.
Otherwise it is third-party tools (listed in the Favorite SEO Tool thread) or proxies.
I am sorry if this is not much help. Would love to know if there is another way, too.