I'll bring this one back from the dead (briefly) since there is a regional rally coming up in October.
The date for the 2016 Show-Me Rally has been chosen and the event will be held on Saturday, October 1, 2016. The rally will remain in Washington County, in & around Potosi, MO.
As for the Rally in the 100 Acre Wood, this is the URL for information about spectating:
Of course, if you sign up to be a course marshal you'll probably end up with a better view than the people at the spectating points. Finding a parking space will be much, much easier and you get to attend the worker's party (free food, beer, etc.) after the rally is done.