So Nike- which has done some cool events here in the past is sponsoring the worlds largest 10K- Labor Day weekend.
http://nikeplus.nike.com/nikeplus/hu...n/joinRace.jsp
You can register and run in one of the many international cities hosting it - or-- you can register and do it on your own. (Not sure how that works because I registered for the Chicago one).
You can walk to- The Chicago one says you have to do 12 min miles (or faster). They are expecting 15,000 here.