I have a significant amount of interest in both the process of scouting and the history of baseball, and if you're anything like me, you're going to love the Hall of Fame's new exhibit about scouts and scouting. It offers a searchable online archive of scouting reports, stretching all the way back to the 1960s. For most players, you can read not only amateur scouting reports from area scouts and crosscheckers, but also ML reports from advance scouts, letting you watch players change and develop over the passage of time.
The examples of amateur scouting include both some notable insights (like this scout from the MLB Scouting Bureau who touted the "size, quick bat, power, [and] arm strength" of a just-turned-18 Bobby Bonilla, while also noting that "defensively [he] seems rough") and some amusing-in-retrospect misfires (like this White Sox scout who envisioned a 17-year-old Chad Hermansen as a "faster and better fielding Jeff Blauser," or this A's scout who felt that while a 21-year-old Jason Bay might be a worthwhile acquisition as an organizational player, his "ability is just short of ML potential" and "eventually [his] bat will hold him back"). I found some of the ML advance scouting just as interesting, as a report like this one on the defensive alignments and trends of the 1966 Pirates give me a feel for the way things worked that I couldn't have gotten from a bunch of old box scores.
You can also search scouting reports by scout, though attempting to click on the profile for individual scouts generated a database error for me. I also periodically got a database error on player searches, though that usually went away if I tried the search again, and I suspect that it might be a function of high traffic on the site. In any event, this page is a valuable research tool and a great way for fans to casually kill a few hours, and I highly encourage you all to give it a try.
If you find anything particularly interesting, please feel free to share it in the comments.