With the Swift Current Broncos he developed (6 years here): Colton Orr, Michal Rozsival, Brad Larsen, Josh Green, and Brent Sopel (+ lots of AHL guys and some cup of coffee NHL guys)
With the Cleveland Lumberjacks he developed (1 year here): Pascal Dupuis, Brett McLean, Nick Schultz, and Richard Park (already had one NHL season under his belt before going to the IHL)
With the Houston Aeros he developed (4 years): Zbynek Michalek, Stephane Veilleux, Jamie McLennan, Brent Burns (coached him 2 years in the AHL and 4 years in the NHL), Pierre-Marc Bouchard, Mikko Koivu, Derek Boogard, John Erskine, Mike Smith, and Josh Harding (Harding only played 151 games, but career cut short by illness and goalies get a limited number of starts) [Nick Schultz, Brett McLean, and Richard Park all played for the Aeros as well]
Coached 3 years for the Red Wings, but I'll just skip them since he was an assistant and you could just as easily attribute positive development to Babcock.
With the San Jose Sharks he developed (7 years) *limiting to young players who improved under him or debuted with him*: Devin Setoguchi, Marcel Goc, Marc-Edouard Vlasic, Douglas Murray, Jamie McGinn, Ryan Clowe (arguably broke out before he got there), Joe Pavelski, Logan Couture, Thomas Greiss, Torrey Mitchell, Jason Demers, Justin Braun, Andrew Desjardins, Tommy Wingels, Matt Irwin, Tomas Hertl (progressed year over year under McLennan, but break out year came after he left), Matthew Nieto, Melker Karlsson, and Chris Tierney.
With the Oilers I'm guessing you can pick out who he helped develop, all of our core players aside from RNH, Larsson, and Talbot; have to attribute some of their development to him and his failures to develop here would be Justin Schutlz, Nail Yakupov (?), Drake Caggiula (?), and Jesse Puljujarvi (so far...).
**tried to keep it to only names I recognized and players who played a minimum of 200 games in the NHL, pretty sure Harding was the only exception I made**
*note with Nick Schultz only coached him 21 games in total between the Lumberjacks and Houston Aeros, not sure if he deserves much credit there*
A lot of players he coached didn't turn into outright beasts, but there are a lot of players there who had lengthy careers. Couldn't pick out a single player in the AHL or with the Sharks who really struggled to develop under him to only get traded and blossom elsewhere, ofcourse a few players got better later on just from natural progression and experience, Ehrhoff is probably the strongest example of one blossoming post McLennan, but he did have his best offensive season to that point under McLennan (with the Sharks 4 years prior to McLennan and was traded after McLennan's 1st year as an NHL head coach), with the Canucks he kept his elevated point production from his last year as a Shark and greatly improved his plus/minus.