Nah, they still do it all the time.
The USFS uses modified King Air 200's as drop planes now.
Here's a cool video. Hard to believe how high he is when he drops his fish.
http://www.youtube.com/watch?v=BkLo5XElVSw
Several western states contract with a company that uses modified Cessna 185's

http://thefisheriesblog.com/2012/01/16/high-sierra-trout-stocking/Here's a good video of the C185 from under the belly
https://www.youtube.com/watch?v=kSpLcs199Z8&feature=player_embeddedAnd of some passes (Way up in yellow on the asi too).
https://www.youtube.com/watch?v=situxqwzgrcSouth Carolina just drops them out of a regular old Bambi bucket, slung under a Bell 205. Looks a lot easier on the fish.
https://www.youtube.com/watch?v=y1LLJkqKkjgedit: I just realized that Chuck beat me to it, and already posted a link to some restocking articles. My bad.
