Kevin Goldstein at Baseball Prospectus has listed his top ten shortstops in the minors (subscription required). Interestingly enough, three of the top six are Angels:
#1 - Brandon Wood - "This year, he hardly gets any attention, yet he's having another great year. He leads the minor leagues with 60 extra-base hits, and is among the Texas League top five in home runs, RBI, and slugging percentage..."
#3 - Erick Aybar - "If these rankings where based solely on most fun to watch, Aybar would win hands down. He's one of those guys who adds style and pizzazz to everything he does, and with his baseball skills, he can do an awful lot..."
#6 - Sean Rodriguez - "currently ranking sixth in the minors in total bases as he's finally found some consistency at the plate to take advantage of a lightning-fast bat..."
As an addendum - Alexi Casilla might have made this list if he hadn't played 2B most of the season.