More of a fun experiment than anything else, but the Pig Shell is worth playing with:

http://pigshell.com/

It's cool, but I always found such things to be cargo-culting and going in the completly wrong direction. You don't want to make a web shell, you want to use normal shell for web.

For a proper "Web UNIX" we need:

- websites talking in structured data (not just plain text)

- less propertiary bullshit (hint: keep sales & marketing people away from APIs)

- ability to conveniently pipe them together anywhere (not on a third-party, complexity-hiding, feature-limiting site like IFTTT)

When I can start typing things like these in my own, local shell:

  @twitter.com/me/tweets/latest | sort > tweets.log
  echo tweets.log | @facebook.com/me/post/new --activity "Feeling: Happy" --photo /tmp/HN.jpg

(where @ is a somewhat general web communication utility)

then we'll have a web UNIX.