I've recently become a baseball fan, though I'm still trying to learn about it - what is the final championship called?
The final game  series is the World Series.  
I know baseball has been around for a long time - when did the professional games first start?
Not sure when it started, but NBC aired the World Series from 1947-1956.
I like to cheer for the Toronto Blue jays - are there any other Canadian teams?
I don't know many teams, but the Blue Jays played the Cleveland Indians and lost at one time
I like watching the pitchers - how far is home plate from the pitcher's mound?  That looks like quite a distance to throw the ball!
Well, home plate is 17 inches, so I guess it's farther than that!