Here's a random idea. The sport of boxing has the following weight
classes (https://en.wikipedia.org/wiki/Weight_class_%28boxing%29):

* Heavyweight
* Light heavyweight
* Middleweight
* Welterweight
* Lightweight
* Featherweight
* Bantamweight
* Flyweight

This might be a useful way to group Scheme implementations as well. A
very preliminary sketch. Comments?

## Heavyweight

(Optimizing native-code compiler, FFI)

Chez Scheme
Chicken
Cyclone
Gambit
Gerbil
Guile
IronScheme
Kawa
Larceny
MIT Scheme
Racket

## Middleweight

(Complex bytecode compiler, big libraries)

Gauche
Mosh
Sagittarius
STklos

## Lightweight

(Simple bytecode/treewalking interpreter, basic libraries)

Chibi-Scheme
Mini-Scheme
s7
Scheme 9
TinyScheme

## Flyweight

(Implemented in assembler, bare-bones libraries)

Armpit
Dream Scheme
Picbit
Picobit
Mobit