Cuis is a Squeak Smalltalk fork, with a focus on reducing system complexity. github 
Some highlights by the main developer, taken from his web site:
''Some of the main ideas and objectives for Cuis are:
Close to the ideas in Smalltalk-80 and "Design Principles Behind Smalltalk".
Includes only kernel functionality + dev tools.
Included code should be of high quality.
Includes a greatly simplified and enhaned Morphic as the main UI.
Easy to fix and extend.
Reasonably stable. Smalltalk kernel should not change much.''
See original on c2.com