This is from Feb 8, 2012, by Keith Law, ESPN analyst:
Keith Law of ESPN has released his farm system rankings. You need an ESPN Insider subscription to see anything besides the fact that former Red Sox assistant general manager Jed Hoyer, with help another former Sox staffer in Jason McLeod, brought the Padres to first overall, but we can at least give you a taste of it. It's absolutely worth reading the whole thing, of course, to get a sense of where the rest of the league is.
The Red Sox rank 18 out of 30 -- not too shabby, considering they lack any kind of elite talent at the upper levels thanks to trades for Victor Martinez, Adrian Gonzalez, and others the past few years.