Personally, I think that pretty much any spot along the parade route is a good spot. I try to make sure I'm not on the inside of a bend*, but other than that, I like most spots I've viewed the parade from (Main Street near Emporium or by Tony's Town Square, in front of the castle, Liberty Square near the Hall of Presidents, Frontierland near LTT and the pin shop).
*If you're on the inside the bend, then you won't see the parade until it passes right in front of you. I try to find a spot where I have a clear view of the parade route for a bit so that I can see the parade coming!