I just found this site - don't know if this has previously been posted (didn't see it when I searched), but I find it extremely helpful for my historical league:
http://home.wi.rr.com/ballpark/02ml_history.html
It tracks minor league team movements and ML team affiliations from 1990 to present. Pretty darn cool!
I'm going to e-mail the guy who put up the page and ask him how he was able to assemble this information. I'd like to take it back further than 1990. Does anyone know of any other sites like this or a good way to assemble this kind of info - other than going to each individual franchise and researching its history one at a time?
Thanks!