CoffeeScript and TurtleScript
Via reports on the OSCON 2010 Emerging Languages Camp, I recently discovered CoffeeScript, a very interesting "dialect" of JavaScript. The original idea for CoffeeScript seems to be to clean up the syntax of JavaScript, while preserving direct correspondence as much as possible. Over time, it seems to have grown more and more "neat features" which have increasingly-hairy desugarings into JavaScript — but the JavaScript translation of a CoffeeScript program is still very readable.
This has some relationship to my TurtleScript project, which also sought to clean up JavaScript to some degree. In TurtleScript I've tried to pare down as much of the language as possible, using the smallest number of syntactic forms and JavaScript features as possible, with the smallest possible parser/compiler/runtime system, inspired by Crockford's Simplified JavaScript.
CoffeeScript has some very elegant simplifications: for example, everything is an expression, which reduces the statement/expression syntactic distinction in C-like languages. Making the body of a function into an expression removes unnecessary return statements. Making for and while into expressions is a cute means to introduce (the power of) array comprehensions without additional syntax. CoffeeScript also has a nice way to express functions both with and without lexical this binding (a JavaScript skeleton in the closet).
Unfortunately, the full CoffeeScript language includes many many syntactic forms — even more than full JavaScript. Some of these can trivially be moved into a library, at a slight cost in compactness. While having varied syntax that precisely and concisely expresses programmer intent is certainly admirable, it makes the language harder to learn and, in my opinion, less elegant. For a scalable, learner-friendly language system I like something like NewSpeak more: a language whose goal is to grow smaller, not larger.