Dan Szymbroski at Baseball Primer has put together a great breakdown of park factors for all major and minor league parks, weighted over the past three years.
One of the things that is particularly nice about this breakout is that he doesn't just show the effect on runs scored, but also hits, doubles, homers, walks, and strike outs. Thus, you can look at the Oklahoma park effects, and see that, while it is a pitcher's park, most of its impact is in the reduction of home runs. This sort of data for the minor league parks can be very helpful in evaluating minor league stats.
I've included this link in my sidebar "reference links," as well.