I used to do this quite often. I found. . .

-several bottles of almost empty to half full bottles of Tussionex (this was the best find)
-crushed Soma ( I remember that one batch I got was partically soaked in coffee, still good though )
-crushed Lortab ( more like broken, most were namebrand )

The thing about finding partially crushed or broken throw-outs is that when you would find one, you were sure to find many

( not so damaged that you could not ID it though )
-various broken benzodiazepines
-lots of pharmaceutical pens and promotional stuff

It really got to be an adventure and I was doing it too much, I finally stopped. But yes, in a nutshell, they do throw away goodies. I made the mistake of telling a less intellegent friend about the idea and he ended up getting caught. He is going trought the legal process right now, yes it's illegal.