There used to be one [0] but it looks like it has since shut down. It seems there is a "Hacker news for $practice" every few months and they have moderate traffic then languish after a few weeks. /r/algotrading occasionally has some interesting discussions. I think that and Nuclear Phynance might be your best bet.

[0]https://news.ycombinator.com/item?id=6844565

I imagine that, given the nature of the business, they don't share an awful lot.