Yes, the classified section of this forum.
Search in "Pets section", "free section" and for "fish" in Craigslist. I've seen fish, such as fancy goldfish, neon tetras, etc., being given away to "a good home". There's also people giving away fish they don't want, or can't handle, or "killer fish" that have killed most of their other fish (probably oscars, convicts, cichlids) and they want the fish out of their tank NOW. Sometimes there's a tank for sale -- with fish -- cheap, say a 10 gallon with 7 assorted fish for $10-15. You could keep the fish you want, and responsibly rehome the fish you don't want.