Many moons ago, I decided to write a Logo interpreter, barely did any research, threw something together, posted it, and then changed my mind.
A couple months later, I started working on Logostack, a stack-oriented variant on Logo that uses postfix notation, kind of a cross between Logo and PostScript. There’s still a lot I want to do with it—including a name change—but it’s finally in presentable form, so here it is.
In the process, I also created the arbitrarily-named Talky, which uses Clumpy to manage asynchronous execution, and also defines a way for additional modules to be written for Logostack. The turtle graphics system is written as such a module. An interpreter for any language could be plugged into Talky, but all I’ve actually written for it is Logostack.
Both Logostack and Talky are in volatile development. A program you write that works today might not work next week, so if you write a program that you really like, I suggest you keep a copy of all the JavaScript code that makes it possible. ;)
Also, some day I’ll write some documentation, but for now, there are a handful of examples in a select menu on the page.