WebSocket-capable applications can now be built very easily. As long as you can write an executable program that reads STDIN and writes to STDOUT, you can build a WebSocket server. Do it in Python, Ruby, Perl, Bash, .NET, C, Go, PHP, Java, Clojure, Scala, Groovy, Expect, Awk, VBScript, Haskell, Lua, R, whatever! No networking libraries necessary.

Stuff already built with this include a real-time Linux stats dashboard, an arbitrary REPL in the browser, and a tool that retrieves SQL data from a server with LiveCode. (Use at your own risk 😈)