socket.io-openfl-client (Dmitriy Kapustin): Socket.io OpenFL client extension. Tested with HaXe 3.x, OpenFL 1.3.0, nodejs 0.10.26 (or dotcloud) on platforms: Flash 11, HTML5, Windows, Android, iOS, Blackberry (not tested).
HaxeNet (ohmnivore): Haxe bindings for ENet, a UDP implementation written in C. With these wrappers, you should be able to release online multiplayer games for Haxe's C++ target.
That's just from my old list, I guess there are plenty more options around Github.