Arkouda [1], [2] is a recent and substantial example use of Chapel. It's a Python package that supports a subset of NumPy operations on distributed Terabyte-scale arrays implemented using a server written in Chapel. It currently involves ~10k lines of Chapel code.
Other recent notable examples include using Chapel for Dark Matter simulations [3], tree-based search algorithms [4], and CFD simulations (to appear at CHIUW 2020 [5]).
Your point is taken that the Chapel webpage could be better at pointing to such examples via a "powered by Chapel" section or the like.