Lambda the Ultimate

I'm trying to find some interesting abstract machines that support lazy graph reduction. Haskell implementations seem to prefer the Spineless Tagless G-Machine (GHC, NHC, YHC), and the G-Machine (Hugs). I've heard that Clean is based on the ABC Machine, but I can't really find any literature on it. I've also seen the machines that SP Jones mentions in his "Implementing functional languages, a tutorial", which IIRC includes: Template Instantiation, the G-Machine, and the Three Instruction Machine (TIM).

I have a couple of questions about this:

1) Are there any other interesting machines out there?
2) Where can I find some information on the ABC machine?
3) Why do Haskell implementers love STG so much?

EDIT: Spineless Tagless G-Machine, not Stackless...

It's common for Scheme programers to develop object systems based on closures. An object's methods are closures whose free variables comprise the object's instance variables. The object itself is represented by a method lookup function. See for example Ken Dickey's "Scheming with Objects".

Have any programming languages been based on closures as the fundamental building block?

The Computer World series is continuing with Anders Hejlsberg on C#. Of particular interest is his discussion of F#:

Q:What do you think of functional programming in general?

I think that functional programming is an incredibly interesting paradigm for us to look at, and certainly if you look at C# 3.0, functional programming has been a primary inspiration there, in all that we’ve done with LINQ and all of the primitive language features that it breaks down to. I think the time has finally come for functional programming to enter the mainstream. But, mainstream is different from taking over the world.

I definitely think that there is a space for functional programming today, and F# is unique in being the first industrial strength functional programming language with an industrial strength tooling language behind it, and an industrial strength platform underneath it. The thing that’s really unique about F# compared to all of the other functional programming languages is that it really offers first class support for object oriented programming as well, and first class interoperability with the .NET framework. Anything we have in the .NET framework is as easy to use from F# as it is from C# as it is from VB – it does not feel forced.

A lot of functional programming languages have lived in their own little world, and they’ve been pure and mathematical and so forth, but you couldn’t get to the big library that’s out there. If you look at languages today, they live and die by whether they have good framework support, as the frameworks are so big and so huge and so rich that you just cannot afford to ignore them anymore. And that’s why you’re seeing so many languages being built on top of .NET or on top of Java as opposed to being built in their own little worlds.

And what he sees as the importance of the entire software ecosystem to programming.

What formalisms are available for specification of visual (i.e., graphical, two-dimensional, diagrammatic) programming languages? Which of these, if any, are popular?
If readers feel that few are popular because visual languages are of limited use, do these readers refute the premise that visual syntax is a superset of character sequence syntax?