The Pennsylvania Farm Show is going on now! The dates the show is open are January 5-12, 2013. You can find more information, schedule, directions, and much more on the web site: http://www.farmshow.state.pa.us/
Admission is FREE, but you will have to pay to park so carpool if you can and split the cost.
Plan to eat a meal there, it's all Farm fresh, Pennsylvania food, and it is good!!!
I have not been there yet this year, but I did go last year and you can see my post from last year here.